ok I dont know if I already asked this here or not but w/e ok you know the back part of the rear seat in a car, the part that folds down, ok I was wondering if it would be possible to remove that and put plexiglass in its place(keeping the head rest for comfort) ok with that there get my subs and put them right near the plexiglass so I can see them hit from inside the car, also what would my box cubic feet be to put 4 15" subs in a car, my trunk is 15.6 cubic foot is that enough