Enclosure help please

[Pork chop]

I'm looking to build a new box for my alpine sws-12d4'S I'm powering them with a mrx-m110, I'm not pleased with the performance of the prefab box, I'm looking to do a fourth order vented through the rear deck, Or possibly a front fire ported sealed trunk (if that makes sense) I set about getting my head around the fourth order and I'm stumped. Do both sections have the same tuning? I'm looking to tune to mid to high 30's and around 1:1.5, 1:2 ratio, seems like the sealed section has to be huge to hit the 30's? Any help would be appreciated