Ethan,
If I place the aft row based on the 38% rule I really have row for one row of seats as the forward row would be at 6 to 7 feet. As you state placing a listening positon at the mid point is not the preferred method but what choice do I have.
Right now if I keep the aft row at 16 feet I am only a little over 3 feet off the back wall. I guess my room dimensions realy are not all that good.
Looks like I will need a lot of bass traping to really kill of all the residual bass.
I am still working on the idea my riser can contain a large amount of bass traping but I may be to new to the world of acoustic design to know what I am really doing.
In the aircraft world when we have to soundproof interiors we rely on lightweight methods. The preferred method is many different materials bonded together to create a blanket that is light as possible to block the transmission of sound. One design we worked on had small internal absorbers imbedded. I need to see if I can locate that file and see if I can recreate cheap enough to make it practical.
Working on the drawing now for the riser mounted absorbers. Should have ready to post this week end.