About the front/splayed walls. Thanks for going out of your way to check those angles. I really do appreciate it. It is something that I did notice and just haven't fixed yet. I also had my speakers at 66 degrees, which isn't really that much of a problem, but I moved them to make a 60 degree triangle and put a couple more pieces in the wall. This should do the trick.
I was thinking of making the addition a slat absorber. Is there any reason I shouldn't? If I was to make it gypsum, I will end up with a triple leaf unless I don't seal it off.
Neil