If you use 1/4 drywall it bends easily without wetting..plus over wetting can lead to stains that will have to be sealed well or you will get bleed-thru
I have a 6.1 Onkyo TXSR600 with a JVC XV M567 DVD...for some reason I do not receive any rear center signal for DD EX...I do for DTS-ES Is it my older DVD player? It states on it Dolby Digital and DTS but nothing about EX or ES