I hear what you're saying. It'll probably be the bog standard version and, as you say not far off the CT version.
The two stats average out quite reasonably, though it's going to result in a set of plans that aren't strictly accurate for either system. The way I figure it is if this isn't good enough for you then don't use them

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I think, they'll fit within the CT 20% rule. I think they'll work fine and I think you'll only really know they're wrong if you take out your ruler and calculator.
Of course I could do two sets of strictly accurate plans, one for each system but the simple matter is, I can't be arsed!
The biggest problem I've come across so far is the M-Drives. T20 and GURPS volumes are very similar in most respects except when it comes to the M-Drives. Gurps has something like 20 tons of M-drive whereas T20 seems to think you can fit an M-Drive in your shirt pocket. Just a measly 2.5 tons!!!!
What I've done is add up the Jump, Maneuvre and Engineering and average that out. It results in an engineering/drive space a little too small for GURPS and little too large for T20 but substantial enough to be believable and should work fine.
I have the volumetric block model made up and it's all working rather neatly. Best of all, all the habitable areas fit inside the wedge shape which was my primary objective.
Crow