I've been looking at different manufacturers and most recommend around 3 cubes for 1 ported 15. I've done some calculations and used 4.44 cubes gross minus around .2 cubes for woofer displacement and also around 56 square inches of port. (Soundqubed's design specs helped, may end up going with an HDC3 15 or HDS3 15) They recommend 56 square inches of port and 20 inches length for a 3.5 net cube box.
After subtracting .2 and .64 cubes for both woofer and port displacement I got 3.61 cubes which would be a tuning of around 36 hz which is very close to recommended.
I calculated the 4.44 cubes from a box calc app which subtracted the 3/4 in wood thickness.
Any opinions on my thoughts? I don't really have the room to do 2 10s or 12s or 3 8s because of the setup with the folding center console and a sub would most likely hit that.