alright, went out and took some measurements of my trunk space that is available for use. its like 40 in wide, 18 in high, and roughly 21 in deep that hopefully will be enough space to use. might have to rethink the amp rack again but whatever. i got a cool idea of ram head cutouts in some plywood and covering it with plexiglass on the side panels next to the sub. so im going to subtract roughly 20 inches from the 40 inches. so i have 20 left to work with.

i ran some numbers with the formula and this is some measurements thatll work :

17x18x20 / 1728 = 3.54
16x18x21 /1728 = 3.5
17x18x21 /1728 = 3.71
17x17x21 /1728 = 3.51

should i make the box bigger than its supposed to be? only thing really irritated me is that the port has to be 19.5 inches in, why i dont know. whats the port depth have to do with the sound of it. unless im not really understanding the whole 19.5" in. port thing. im thinking from the face of the box the port has got to go back 19.5 in. but i should leave a couple inches also. little help on that one if u could. i made a little picture of what im thinking about doing.