L 7 squared !

i have an 01 also and i messed with that forever, and even put 15's on the seat haha. but ultimately best solution was to remove the back seat and make a false floor. has worked great for me. and ive had 2 12's, 2 15's and 2 18's back there before. i suggest that but you can still probly flip the seat up and make a small false floor and then make your box taller vertically. like this, when i had 4 tens sealed... I have an 01 dakota that I took the rear seats out completely.My box would not fit with the seats folded up.I have a 8 cubic foot box back there with 2 -15" solobaric squares. No problems with it fitting at all especially if it is a quad cab.I did however have to tie them in to keep them from moving around also. Good luck with the install!!

Heck yeah ! that would be a blast to build! good luck and keep us posted !!!