It's a little late to think of this now, but I wonder just how complicated it would be to add say 6"-12" to the height of a "completed" CTC? Obviously, not a preferred operation at this point, but....Even 6" would make a huge difference in comfort when standing and moving around inside. Also, this could be an opportunity to add some "Daylight" at the top of the wall with some "glass blocks" or something similar. It wouldn't be fun at this point, but if a person was to do this first, I can see where you could get a very custom result. Someone out there with drafting or art skills maybe could render us up a drawing? I envision cutting the roof spars at wall top plate and extending each 6-12". Then installing blocks of Lucite or similar that are 23"x6"-12"x 1.25" WHD. in select areas or all the way around at the wall top plate. That would add a lot of daylight inside and might be an interesting effect at night from the outside...
Whaddya think?