Box design/tuning for (2) dd9918s sc ?

dual dd9918s sc dual 2 ohm

i drive a silverado ext cab (no back seat). i prefer subs forward port up across back wall of box

my power 3-batts(2-2000 kinetiks,1-2400 kinetik) next to cactus 5kw amp, 300 excessive amp alt, big 3 and all power and ground zero gauge kicker flex, i xstatic 2000 batt under hood, amp will be wired to .50 ohms.

i compete in meca and usaci. thank you