Thanks for your response.
My room is 15 ft wide. So 1/3 would be 5 ft from one side wall and 10 ft from the other side wall.
So from your response, you would have the sub 1 in from the solid wall and since the sub is 17 inches wide, that would mean that the woofer is about 6 inches from the grill cloth for the 24 in false wall space. What is the minimum distance between the woofer and the grill cloth. If I can save a few inches, I might do so.