update & new thread, im not doing 3 15" xcons in a 4th on a 3500 anymore.
i bought 2 dc level 3 18 m2's yesterday for a ported wall.
Someone recommended a shop ive never heard of, 15 minutes away, and i just got back. finally ive found a shop that knows how to do what i need. these guys know their stuff big time. they had some intense car show stuff going on and knew as much about boxes as me.
they can work within my budget of 650.
the owner recommended 1.5" thick MDF (yes - 1.5"!), saying 3/4 would flex hard.
my original idea is good and theyll use it (build box, put through door, built port in the car). it should come out to about 13.5 cubes. angled baffle. i couldnt be happier.
i also put a b stock RE xtx 5000.1 (2500W @ 1) on hold for a couple weeks.
all i need is .. $1000!