I'd like to build a double wedge box for 2 12" RF PS1's they got low rms (already had da amp). I would rather use plywood. Rockford Fosgate has the cool box wizard tool for subs that does all the volume math, but they use "mdf" in build materials. This is going on the back bench of my x-cab Tacoma. If I use 5/8", will save only few inches. Would it be strong enough? opinions please.