I'm working with very similar room dimensions in a video edit suite and have similar questions. The primary and secondary room-modes are 69, 81, 57 and 138, 161, 114Hz and the editor faces into a corner - with a 36"x36" glass window immediately to the left.
My plan is to use 4" thick 703 straddling the front and rear wall-ceiling corners but I'm concerned with how far the 4" panels on the walls stick out into this already small-feeling room. How much am I compromising by using 2" thick panels for the lateral first reflection points? I would also take them out of the frame and bevel the edges which leads me to wanting to use a denser panel for more durability.
I'm eager to see what the other forum members think. I'll be searching for relevant posts in the meantime.
PS: This is my first attempt at posting an image. Let me know if I should resize it.