Another question: to clarify, the hemi-cylinder diffusers are 12" deep per Toole's recommendation. I'd plan to install the surrounds flush with the outermost edge of the diffusers, so this would effectively need to be a 12" deep false wall per as shown in my chicken-scratch drawing.
Do you know of any example installations (hopefully with pictures) of door on such a deep wall? Is it going to look/feel ridiculous trying to install a door in such a wall?
Thanks for all of the great advice.