It looks OK to my untrained eye, but it might be worth asking someone like Ted White or Dennis Erskine what they think. Considering you've got a limited space to work with and can't use an inch of foam, it looks like it might be your best choice.
I once used foam backed carpet on the lower side walls to tame the slap echo in my last HT and it worked well. The trouble is I've no idea what it was doing overall as I didn't measure the room in any way, so although it removed the echo, I reckon there was lots of room for improvement using the correct products. It could be a cheap alternative but a pain to remove if it doesn't work.
Originally Posted by elmalloc
Who says Cameron is "right" and why do we care about him so much - lol!
I trust Gary Lightfoot more than James Cameron.