It's tough either way, I think i'd have to add additional levels instilling the power into the bond in order to use it multiple times, and of course I'd have to do that for a collar. One good thing as it's ReAn I'd get a decent bonus for compatible Arts with the familiar bond.
When I made Seven League Bound and Bound of the Homeoming for Eilid, I used the equivalent bases from the Rego Corpus, because everything I looked at looked like it was about the same for Co and An.
And the base Individual for Animal is up to Size +1, the size of a pony. A full-fledged horse-size would be +2 (and +1 Magnitude to the spell).
Here's an idea. Instead of giving Alexei the Here, Boy spell, why not give it to Donar as either a power or something to be enchanted into him? That way, it's R: Personal instead of R: Arcane Connection, and since magus and familiar are (I believe) Arcane Connections to each other, he can always go right to Alexei? Otherwise, the way you have it, it's going to be a Ritual spell...pretty bloody useless, I would think.
That might be the way to go, though it shouldn't be a Ritual spell; if it's anything like an instilled effect, then the level 50 cap doesn't apply, and none of the other Ritual requirements are there.
1st: Regoing an animal might be easier. I'll have to check.
2nd: Yes, but there's another way to do it. Open an Intangible tunnel. Cast a teleport spell at touch range. That saves you 3 magnitudes. You can invest this in the bond, also, which gives you a +5 to enchantment.
Actually, Base MM is 10 (size 0 dog).
He then bought the Gigantic quality to increase its size, but this doesn't retroactively decrease might 
But yeah, Alexei needs to be modest, here.
And yeah, he'll need an extra magnitude for Size 
Yup, you're right.
Thing is, this is quite hard. I considered it, trust me. And at best, it'll suck his might dry. No, really, an invested effect is probably the best way to go. Hey! Here's an idea! Why don't he and Isen collaborate on this? Isen, too, would be interested by a thing like this! 
Rego 26 + Animal 05 + Int 02 + MT (rego) 7 + Aura 5 + Rego Aura 5 + Helest 7 + Lab 1 = 58
Add + 8 for Alexei, that gets to 66.
Still not enough to do it in 2 seasons
Use the power Humans are easily misplaced ( RoP:M pg 71) It requires an AC but as a familiar it already has an AC to Alexei. It is not TP but that could be done later in an enchanted item.
See, now, this is why I prefer Bjornaer. Making magical animals suuuuucks.
I only find it hard because I do not know what a mythical dog might be at this period. Personally, I would make a magical mastiff that is a very good watch dog. Based on the breed being camp watch dogs for the Romans. If you want a hunting Dog the Hound of Virtue is a great template.
What it is and what Alexei wants it to be might be different.
Well, surprisingly, I'm finding it to be rather enjoyable and relatively easy. The worst part are the animal's base (mundane) stats, but, hopefully, one can manage with available ressources. Then, of course, one has to restrain his choices, but this is part of every character creation, working within a framework, and this has this advantages, since it forces you to focus on a concept.
To be franck, I like a lot the template I proposed to Jebrick for Donar, as he is both a redoutable combatant, a great tracker and a pretty good watchdog. Or course, he can't teleport or such, but not only are these outside the base concept, these are major powers, whereas he's just a might 10 beastie (which is, when you think about it, pretty weak vs hermetic magic, and even pitiful when faced with Might Strippers)
Might Stripping a Familiar...oh yeah...that's war.
Wouldn't that be considered a high crime (outside of a Wizard's War that is)? Depriving a wizard of his power?
You can buy more might if you want. It is a minor virtue. It just makes it harder to bind as a familiar.
Still tinkering with helest's powers, I have everything save the final touches (have for quite a time, actually), aaargh!
Totally.
Given the bond magi share with their familiars, the reactions to this would propably be quite harsh anyway.
In fact, I wouldn't be surprised if systematically doing this in WW was frowned upon, especially by Flambeau magi. After all, this is akin to striking at your ennemy's family instead of him. It can happen, and be useful, but it's not something you do as a default, especially when you value honor and "fighting like a man"
Not that this makes much difference... I mean, assuming you've got a Might 20 familiar (which is far above the average), it's still easily killable by even junior magi.
So if facing WW? Take great care of your familiar.
Apropo of nothing...
Why was my immediate thought on seeing this, "Uullrrriiiich?"
So, there's been a lot of OOC commentary but not much going on with the stories? Do they suck? I think they are all stuck waiting for the players to move events forward...
I am right in the middle of changing jobs. My post rate is suffering. I expect it will improve starting next week 
I've just had a rough week. Doctor visit Tuesday (no insurance, no job, sinus infection and high blood pressure). Been thinking about it a lot, but just haven't mustered up the energy to do much. It's on my agenda, though. Just need to go through and see what I need to respond to.
Didn't you just do that?
I did. I took a contract position while I kept looking for a permanent job. Contract job has a very restrictive firewall, hence my having to post by phone. I expect that to change next week.
Well, I've been much less active than normal in the last few weeks, and I noticed everyone else had been, too. I'm going to be pretty busy for the next month or more, so my post rate will probably be about 1 post per story per day. OOC is going to be hit or miss. I just wanted to make sure that people were in stories that were interesting to them...
Oh...just assumed you were too busy JL, that's why I've been slower. Some things going as well, i have family in town and today is the anniversary of my dad's death, so mind's a little occupied,
But mainly I was waiting on you (and not impatiently you said you had a ton of stuff on your plate), and so far it seems that Fiona is the best at Auram, but spontaneous could be an issue.