I just bought a 1222D 12" type r and I'm having problems building the enclosure. I want to place the sub facing the back of the rear seats, so that when I drop the seats down all you see is the sub. I figured out the angle (25 degrees) for which the sub would sit at. The problem is the rest of the box and dimensions using this angle. I can't leave my car without having a nice system in it...(pic attached). Any assistance would be greatly appreciated.