Hey there I trying to design a box to go in the back of a 96 ford ranger extended cab. I'm wanting it to sit on the little 6" curb to utilize the floor space for cargo and passengers legs. I also want to be able to use the rear fold down jumper seats which leaves me with about 16" in between them in the center. The highest I want to go is 21" which is at the lower edge of the rear slider window. The sub I'm using is the JBL GTO804. I want it to have the .6 cf (it's what's recommended). With a slot port tuned to 33 hz. I want the speaker front firing and the slot on top pointing up. I have come up with some box dimensions but I want to be sure I'm on the right track. Anyone have any suggestions or criticism??