Right now I have my 15" PBX SQL in a prefab box by memphis. It is slot port with about 3.5 cubes, I have no idea about tuning. Well heres the problem.. It sounds decent but the sub is facing up and I want it facing toward the rear of the car (97 taurus). The box I have now will not fit. I know that PBX recomends 3.5 cubes of space max and 2.4 cubes minimum. I would like to stay around 3 to 3.25 cubes for SQ and SPL. I still want to stay vented and tuned at about 30hz. Any ideas on how to build this box will help. Oh yeah by the way the memphis box is 31.5 W by 18.5 H by 16 D. I need all external dimensions to be about an inch to and inch and a half shorter.