Helped a friend pick out gear last spring for a '13 Avenger 4 door(trunk, fold down seats), ran into this issue as well. I tried talking him into letting me build the box in the trunk, firing forward and sealed off but no go. We settled on 4.5 cu/ft @32 hz for two ZCon 12's (subs up, port to the side) on a single SQ 2200 (until he finishes upgrading his electrical, then it will be two, strapped) and it's quieter than my two XCon's on a SQ 1200, but still clean and precise. Going to try a different box here soon. Any specific strategies you've used to combat 'Dodge Bass'?
Also, I'm not much for Mustangs.. but that's nice.