Looking real good!
I have about the same size theater as yours, and saw in a few pics HVAC into the soffits....
I have to punch into my main floor supply to my theater and was wondering what ductwork you are using...can you get it at a local home depot?
Also would like 2 rows of seats for a 100" wide 16:9 screen, but am afraid the front row would be too close (mine would be about 9 feet from the screen) if I used a 6 foot riser. Could I get away with a shorter riser?
Good luck on your build!