That isn't my room, here is why my room currently looks like:
My target goal is to have the visible screen be about 3" in from the ceiling soffits. So with frame, that is probably right at that inner mark. That leaves about 19" from the sides of the screen to the wall. I am sure that if I put the fronts of the speakers close enough to the back of the false wall, the main sound will probably be just fine, but with speakers with ports in the back, sound will fire towards the (treated) real wall and if it isn't absorbed, it could bounce around behind the screen. I also have 2 subs (not small) to fit back there... Maybe it is just a bad idea.