A tower conjured with Conjuring the Mystic Tower is much larger than that, I think. The description of the spell states that is is 80 feet tall and 30 feet wide. So unless each floor is over 20 feet tall you are missing a few.
Also, splitting your lab on two floors comes with some disadvantages, according to Covenants p.106 specifies that a lab must be a single chamber. Splitting the lab on two floors would probably give it the Minor Structure flaw Awkward Shape.
The tower is also a bit wider than the spell provides, so I thought it would be a wash.
My understanding is that the "upper part of lab" means that the lab has a ceiling that is twice the height of the ceiling in the other rooms. Thus, the "upper part of lab" refers to the open space above the lab. Same for the Great Hall. That's a double-height room. so there's a hollow on the next level up above the great hall.
Thyra would want the Orthanc 
one solid mass of stone rather than blocks
Galan doesn't have strong feelings about whether his tower is smooth or made of individual stones. I kind of figured that CtMT was a solid mass of stone, but I suppose that was just an assumption on my part.
I don't think that the spell's parameters can be changed in order to have modified proportions.
Double-height lab and great hall are certainly possible. That would make it easy to install the Gallery minor virtue (+1 Safety, +1 Aesthetics, +1 Teaching) into the lab, perhaps even have it incorporated into the design right from the start.
The spell's description says that it is a single block of stone, but it might be textured to look like it is made of individual stones.
As I said, it's really just fluff. I can't imagine it would have any real game effect. I was just pleased that I found tower floor plans that were relatively close to the proportions of a mystical tower. I thought it might add some verisimilitude to the game. The odds that I could find plans to an authentic 12th/13th century circular tower that was exactly 80 feet high and 30 feet around are infinitesimal.
That having been said, it is only fluff. If I can't do it, then I'll probably just abstract my tower and leave it at that.
That was my thought.
I'm personally fine with finesse ability allowing one to vary the composition of a spell beyond a predefined static ideal that is set by a spell. The longer I play, the less rigid I feel like being with respect to Hermetic Magic. It has plenty of limitations, and those limitations are interesting, but honestly, a spell to create a tower that uses vis (a player resource) isn't a place I find interesting to be limiting. If players want to spend resources on something, they should get what they want out of it, by and large. Now, nothing should be for free, there should be some element of risk, and that's where the finesse ability comes in. And a botched finesse roll won't mean a destroyed tower, but it will mean that there's something wrong with it, somehow, which will probably show up in the lab...
If I have to risk a Finesse botch to get an authentic tower, then I'll take a pass. As I said, I was just doing it for color, to give the game more of a medieval feel. Granted, the risk is low. But that's still 7 vis and the effectiveness of my lab we're talking about gambling on a roll. Why take risks if they're not necessary? If a standard cookie-cutter 80-ft tall by 30-ft wide tower can be done without a Finesse roll, then I'll play it safe and boring and go with that.
Before you jump to conclusions, keep in mind the following.
Just want to clarify to the players, there isn't a regio entrance as a boon or hook of the covenant. The portal was created to cross into a higher level. I'm knot going to use this in the feature to drop stuff on top of you.
You might think of it as a compromise, but imagine yourself being put to sleep, unable to defend yourself in any way, reliant upon strangers who just put you to sleep. So, yeah, he can view it how he likes, however you might not like how he views it.
Also, I'm going to point out that no one at any time attempt to do perhaps the most obvious thing. Talk to him. Yeah, magi have magic at their disposal, but they should still speak with their guests, even the guests who appear to have been acting rudely.
Galan was talking to him as a guest, treating him very courteously, inviting him in and bringing him to his own tower to rest.
Brag made a request, Galan pardoned himself to talk to his compatriots, a reasonable reaction, I think, and the next thing Galan knows, Brag has opened a gate, is gone, and is out of earshot. From the time Brag opened the gate to the time Galan was able to reasonably act (beyond a moment of observation), Brag was nowhere that he could be talked to. Even shouting, Brag was too far away to be talked to.
All Galan did from the time that the gate was opened was look at the gate for a few moments and rush over to it. By the time that was done. Brag was outside of shouting range. Galan tried to bring him closer so they could ask him what was going on. That didn't work. So he tried to slow him down so that they could catch up. Everything he did was a measured response to the situation.
When exactly was Galan supposed to talk to Brag after he opened the gate?
I said that he was outside of Voice range of Hermetic magic, normal or shouting. I did not say out of shouting range. There is a distinct difference, which has been discussed a fair bit, though perhaps not everyone is aware of the distinction (mea culpa). In the span of just over a minute a gate was opened, magi talked amongst themselves, and then spells were cast at the individual who opened and went through the gate. It may appear to be a discourteous act, but no one knows the nature of the opening, whether something from the other side can cross over, or even see the gate on the other side. You don't know that it was, in fact, discourteous, though it's understandable that one might think so, but then one would thing an utterance of "How rude!" would be more appropriate than zapping the creator with magic. No one knows anything now, except for the info he provided, and all of you view it as suspect information.
So, here's what the magi know. A being (human, faerie, unlikely to be a hedge mage with what appears to be resistance) of significant power asked for permission to enter the grounds of the covenant, he then opened a way into what is presumably a regio, if not the magic realm. He had two companions that were unable to cross the Aegis boundary. We can dispense with some of the after action discussion and the magi know he resisted a Mentem spell with 6 magnitudes of penetration. You know that he closed the gate, or it is in the process of closing, if someone wants to jump through it and discuss things with Brag. He told you that the plague has something to do with the Magic Realm, and House Merinita is the least affected House in the Order. You know, or at least can assume with a high degree of certainty that the spot he opened the way was his intended destination. There is no Order of Odin, and apparently the magi with the plague will be coming back, at some point. It also appears that he took advantage of the distraction of the magi to open the way to his intended destination, and could have closed it the moment he and his companions have crossed. Also, you, the players, know the title of the thread.
That being said, this opens plenty of opportunities for everyone.
Truth be told, the same could be said about him. True, he's a magus/hedge mage/magical being who has magic at his disposal, but he should still speak to his hosts about his needs even if the hosts appear to be acting cautiously.
Instead, he waited until our backs were turned and used his magic to get what he wanted without negotiating with us.
Some of us, Galan included, were willing to talk with Brag and were trying to do so. Galan was being entirely courteous to Brag and arguing that we should negotiate with him to see if there was a way to gain the information he had. I designed Galan as a talking-type magus. I sacrificed a major hermetic virtue to get the Gentle Gift. I was trying to be the negotiator. But then that option seemed off the table. Brag had walked away from us and was gone into a regio/Magic Realm beyond our ability to communicate with, possibly forever. Galan just wanted to get him back to the negotiating table.
Now maybe it was rash to cast a spell. For all that I've been on these boards for a while, my actual experience with Ars Magica games that go for more than a couple of months is pretty slim. But Galan was just trying to get Brag back to where we could talk to him again.
I was not aware of the distinction. When you said he was out of Voice range (even shouting), I assumed that he was out of range of communication.
I used very precise language for Brag. He was clear, that he was at his intended destination. He also told you what he needed. He didn't tell you what he was going to do if you agreed to his needs, or even if you didn't (open the portal). It's a bit of a distinction, but he told you his needs.
It's not as if he hid what he did, it's rather likely he could have put all of the grogs to sleep, or otherwise hidden his actions, you don't know what kind of power he has, but being able to do what he did is Power with a capital P.
Ultimately, though it comes down to the issue that the magi were confronted with a choice of doing something unknown. Following Brag, one way or another it was going to happen based on the course of events that unfolded. Even with casting the sleeping spell, someone was going to have to cross after him and follow, right? That choice of following may still be there, it's not clear if the portal will deposit you at the same place, so there's even more that is unknown. Add to that, if you do follow after Brag, if that's where the portal takes you, you still have to deal with the explanation, and you'll have to find a way back. The portal will remain open for an indeterminate amount of play-time. Giving all of the magi a chance to go in or demur. The first magus who goes in, will, in game terms, allow others who respond to posts more slowly the opportunity to join up. Another factoid to add is that none of the trio were carrying much that you could tell in the way of supplies.
The limits of Voice range are due to the fact that it is becomes theoretically possible to extend Voice Range out to absurd ranges with Imaginem spells. Low level Imaginem spells, to boot. People, can and do shout across fields and can be intelligible.
Well, for good or ill, Galan has gone in. He wants an explanation for what's going on and a chance to find out if Brag really does know about the plague. If Brag kills him for his impertinence in casting a spell on him, so be it.
I'll keep that in mind in the future. (So many past threads and never enough time to read them.)
(Btw I'm here but irregular at present, apologies)
Greetings Gentlefolk!
I discussed with Jonathan, some weeks ago, joining this saga. I'd still like to do so, assuming that the group is willing, and their is space. I've been away from home for over a month (no books, sniff 
), but I will be within reach of them in under a week, so I'd like to be thinking about what line to take. I was going to try for a generalist, but Jonathan sagely advised a much more focussed character. I'd be happy to receive direction from the group about the perceived needs for this saga.
Some thoughts I had had (in no particular order):
I'm not wed to any of the above, especially if somebody comes up with a very amusing idea...
Regards
Domazhir