Here's a little sketch of what's going in my van sometime during the next few weeks, after it warms up some. I over compensated a little for the bracing I might add. Which will take anywhere from .5 - 1.5 cubic feet. So my enclosure volume may go up and tuning frequency may drop but its going to be between 35-36 Hz and 24.11-25.xx cubic feet net.
[box] Outer Dimensions
Height: 41"
Width: 52.75"
Depth: 35"
[Port] Inner Dimensions
Height: 39.5"
Width: 14"
Length: 20"
Equipment
Subs: (4) Digital Designs 3500 series 18s Dual 2
Amps: (2) Hifonics XX Maxximus 10,000 rms @ 14.4v