Well, of course Onesiphorus would make tons of money with the boat. Sharing it, on the other hand (avaricious)... 
Japik would be more concerned about the crew. If they start complaining about not getting their fair shares he won't let him use the boat.
The core rulebook is a bit limited when making a companion character as more than half of the flaws are hermetic and many of the general flaws are quite boring when you want to create a decent character.
So I wonder if you would allow 1 or 2 virtues/flaws from Grogs as there are quite a few interesting ones.
As minor general virtue: Craft Guild Training; works like Warrior or Educated, 50 xp that must be put in Craft, Profession, Bargain or Organisation Lore: Guild.
As minor general flaw: one of Hallucinations, Lingering injury, Sleep disorder or Unlucky.
Note that I don't have Grogs, so I can't look up those virtues and flaws to get the details. Perhaps you could send them to me by PM?
I wouldn't see a problem with Craft Guild Training, if it is simply a 50 xp virtue. That's fairly standard, with just a different focus then the similar virtues from the core book.
I'll have to see for the flaws you list. From their name alone, they can probably be reworked as a Lesser Malediction.
Here is a first draft of my stonemason companion. Lacking a few virtues and maybe another minor flaw plus some specialties to fill in.
Lothar the Stonemason
Characteristics: Int +2, Per +2, Str +2, Sta 0, Pre -1, Com +1, Dex +1, Qik -2
Virtues: Craftsman, Craft Guild Trained (if allowed), Dowsing, Puissant Craft(Stonemason), Reserves of Strength, Well-Travelled [lacking 2 minor virtues for balance]
Flaws: Dependent (two children), Compassionate (major), Driven (minor) [I may take another minor general flaw.]
Abilities: Area Lore: Bavaria 1, Area Lore: Lower Saxony 1, Athletics 3 (heavy lifting), Awareness 3, Bargain 3 (construction work), Brawl 4 (punch), Carouse 1, Craft: Stonemason 5+2, Craft: Blacksmith 4, Craft: Woodcraft 3, Dowsing 3, Etiquette 2 (craftsmen), Folk Ken 2, Leadership 3 (leading craftsmanship), Low German 4 (craftsman's vocabulary), High German 5 (Bavarian), Organisation Lore (Stonemason's Guild) 3 (Personalities), Survival 2 (hills), Teaching 2
Lothar was born in Bavaria close to Regensburg. His father was a wandering thatcher so he has travelled quite a lot from his childhood. Being strongly built and getting an interest in buildings from his father he got an apprenticeship with a master stonemason when he was 12. He has also developed some skill in blacksmithing and woodcrafting. During his time as journeyman he travelled north and spent a lot of time in the coastal towns and cities of Saxony. There he also met his wife and got two kids. Only two years ago his wife died in a disease and since then he have had to take care of the young children (5 and 7) on his own.
Ever since he was young he has had a knack for finding things. It's nothing he really thinks about as supernatural or magic, he just knows where to look and what to look for.
Yes that was what I thought as well. We can call it Lesser Malediction and then go by the description in Grogs if you allow it after I have posted it here.
Craft Guild Training is just 50 extra xp that must be spent on the Abilities I listed above. But it also feels solid background-wise.
I just checked the City & Guild book and there is more detailed Social Virtues for Craftsmen. Guild Apprentice, Guild Journeyman etc. They are all minor virtues.
I would like my character to recently have past his test to become master of the Mason's guild. If you rule that it cost a minor virtue for that I will take Guild Master otherwise I stick with Craftsman.
If you are still interested in developing the concept, let's start a separate topic for the character. Use the first post for the stats, as usual.
Thanks Bearlord!
I already thought a bit about my Magus:
We already have a Bonisagus, an Ex Miscellanea, and a Bjornaer. I think a young covenant like ours will need a lot of connections to different houses. So I am thinking of a magus from a different house.
A Tytalus is too un-relaxed for me. Verditus often have problems with spontaneous magic. FlambeauĀ“s are too aggressive. Chriamon?? Hard to play this enignma stuffā¦but interesting.
Guernicus ā¦..Not for me. The quaesitorĀ“s should be under control of the SG. Same for a redcap.
Tremere are typically too disciplined and Jerbiton deal too much with the mundane world.
Finally I came to a concept of a Merinita with strong Faerie Blood (undine) and an affinity to Aquam Magic.
Grown up in Irencella he feels a strong desire to for the sea. So far only one in his live he has seen the coast. Eever since then he wanted to come back to shore and feel the salty wind in his Faceā¦.
Shortly after his gauntlet ha will try to make his way to the next coast.
Thatās not very much details by I will add more details it in the next days.
Feedback is welcome! 
The concept sounds very good to me.
Didn't Joel's character (the Bonisagi) spend some time at Irencillia and he has a faerie friend as well? Maybe your charcter could have some connection with him?
We could certainly need someone with strong Aquam? I'm doing good in the water as dolphin but I chose Deficient Aquam just to twist myself 
If you choose to play a Merinita, one thing you need to be aware is that in this saga the faeries are generally dark, strange and twisted beings. They will often take the role of antagonists to the magi. Even the "light" faeries are strange and disturbing to humans. And seamen have many more stories about dark monsters than they have about peaceful sea creatures.
So if your character has faerie blood, this will be considered an inhuman taint by most mundanes. Thye normal Faerie Blood might not be too bad, but with Strong Faerie Blood this will be more pronounced. Churchmen might very will call it "unholy", but in general this will make it difficult for your magus to interact positively with mundanes. This will exacerbate the effects of The Gift on them.
This is not to say that the concept you propose cannot be fun to play. I just don't want you to stumble into in-character problems that you did not expect as a player.
Yes, Herman spent some time at Irnceilla, and Aerianos is a faerie who is his friend. (I need to copy the description of Aerianos to the right place in Herman's writeup.)
The Idea was to ācoverā the Faerie with some Imaginem (Disguise of the Transformed Image). As far as I know the effects of the Gift cannot be covered by magic. But is it possible to let a strange looking person look normal? Ok due to the Faerie Upbringing the ānormal lookā made by use of the disguise might be still strange. But thatās part of the game. And I hope the magus will learn by the time to use its imagine magic to look a bit less faerie like. I donĀ“t want to have such magic all time active. Some people including churchmen might see trough this disguise.
I can also use mundane costumes to look less like a Faerie.
To bring it to the Point: As long as I have a change to deal with it (including some extra effort from my side) without risking my health right from the first moment, IĀ“m ok with that. 
Beside from the Faerie Nature I have some other Questions:
Would the magus be just after gauntlet (age 25)? Or is it possible to have 1 or two years exp? I have no preference, just want to know.
Does a magus have to penetrate his own resistance in case he is using touch range or other ranges than Per.?
If yes:
Would it be Ok to take some (more than 2) standard Spells (ArM5) and change the Range from touch to Personal?
All of these can work to some extent. But each has its drawbacks and limits. It's not like this covenant is set in an isolated forest. They have mundanes at their doorstep. Including hired servants working for them. So anywhere outside of his sanctum will be risky.
Yes, your character will have the chance to deal with it. But it would be a constant effort, and constant risk, particularly if he doesn't want to be constantly covered by Imaginem magic. I would expect you, as the player, to constantly infuse your posts with the fact that he needs to hide his true nature from the mundanes. This would represent the tedium (for your magus) of needing to live disguised almost all of the time. As you say, that would be part of the game -- if you slip up too often or for too long, I will have to have some mundanes react negatively and causing trouble. The question is: Is that the kind of gaming experience you want?
There can be a few years spent past Gauntlet, or not. Depends on what you want. Any time spent after Gauntlet will not use the advancement rules. More on this when you have a complete magus right out of Gauntlet.
Yes, a magus needs to penetrate on himself if the spell has a range greater than Personal.
I might allow 1 more spell to be a R:Per variant (bringing the number of non-standard spells to 3), but no more than that.
One important thing you'll need to think about: Why would your character be willing to join a band of outcast/renegade magi? Their covenant is not recognized by the Tribunal. It is, in fact, a secret covenant. It is also resources-poor -- in terms of both mundane and magical resources. So why would your magus be willing to break away from more traditional covenant life and its comforts, not to mention hide his true nature most of the time?
Thanks for this feedback.
I totally forgot/ignored the mundane people being close to the covenant. Too much problemsā¦.
I will think about another concept and house. Maybe a Tremere who feels his house (and the Order) need someone to keep an eye on the northern border of the Rhine tribunal. The other members of his house disagree with him. Finally forcing the young magi to go his way.
Jerbiton would work as well I think. We could use a gentle gifted magus.
If Arthur is OK with a gentle gifted Jerbiton I will create a Character concept.
Normally Jerbiton are more concentrated on Me and Im to deal with the mundane. For both arts we already have specialized magi. So I would have to go for an untypical Jerbiton.
At the moment I have no good Idea for a character concept. 
Anny Ideas 
I think as general recommendation you should try to go for a house and make your character a bit untypical for that house since that would make the character more likely to want to join a rebel-sort-of covenant like ours.
Maybe a Gentle gifted Flambeau with specializations in Aquam and Ignem? Not so aggressive as Flambeau sometimes are. Maybe with some other connection to the sea?
Just an idea.
Slowly there is growing an iIdea about a gentle gifted Jerbiton. Tomorrow I have a few hours sitting in a train. This will give me time to write it down.
Torros ex Jerbiton Character Concept
The boy who would later became Torros was called Peter he grewd up in the grater alps as son of a goat herder. As strange thinks start to happen in the presence of the child Peter was given to a traveling noble men called Jorgus.
Jorgus was a Magus from the house Jerbiton. He found that peter was gifted and took him as an apprentice and named him Torros.
Torros had the gentle gift but also problems with the arts of Terram and Herbam, he was very interested in the work of stonemasons and wood carving. He tied to learn wood- and stone carving but never managed it do produce anything better than ordinary looking results. His hands were not able to follow his mind.
Finally as his lessons in the magical arts came to aquam it came out that this was something he could handle very well. For two satisfying winters he used his ReAqu to produce beautifull Statues made from Ice. During this time he also discovered that he seems to have a good immunity against could, letting him work for hours in freezing cold winter air without any problems.
All his work was melting in the sun of the following spring.
Beside his activity in the mundane art he managed it to finalize his apprenticeship successfully. The elder Jerbintons told him to leave because the number of Magi in their covenant is strictly limited. Jorgus gave him some Silver two Grogs and all his best wishes. The two grogs named Hans and Franz are one Guard (Hans) and one personal Servant (Franz).
So Torros started his new live as a Journeyman, a free Journeyman. He starts to travel North, because he had heard in some Stories that far far away in the North there are Hills that always covered in Ice. Everlasting Ice, Ice that can be formed to artworks, everlasting artworks made by Torros the great artist.
By the time traveling North he learned that his silver will not last forever and he has to take care for his Grogs too. Both of tend to feel chilly and get ill as soon as winter is coming. Torros changed his plan slightly. Instead of searching for the everlasting Ice he will try to find a covenant that gives him the resources of building an iced chamber filled with his artworks.
So first he will try to find a covenant and then try to learn enough about PeIg to chill a room cold enough to prevent his artworks from melting away.
So, in short, the concept is that of a Jerbiton ice sculptor (but deficient in both Terram and Herbam) who wishes to create/find a chamber where he can keep the temperature low enough so that his work doesn't melt?
Some questions:
- What will he do when his chamber is filled with ice statues? With magic, it doesn't take long to craft a statue. He could presumedly fill a large chamber with his work in a single season.
- The covenant on Helgelund doesn't have much space. How do you (the player) see this as compatible with this character's goal?