I simply stated that a sub sitting on ¾" of MDF will never be supported as much as it would be if it were installed on both layers of the ¾". And, with subs weighing as much as 80 plus pounds, I don't understand why people don't install on top of the double ¾". I'm a field guy, not a pencil pusher in an office type. I'm the one who the engineer would ask, "well, what do you think will work?" That's why the blueprints would usually say, "engineer not responsible for drawings", "not for construction purposes", and "field verify all dimensions." Engineers wouldn't even take responsibility for their own drawings. So, being an engineer doesn't mean jack to me. I build the shiit, and, I know what works and why it works. Because, I've built it, repeatedly. I don't scribble on vellum in an office and call myself an engineer. Most engineers can't even hang a picture.