I’m needing help with a subwoofer enclosure design for 4 Skar ZVX 8 d2. I’m running them at 1 ohm with a Skar rp 4500.1. They are going in a 2003 Chevy Avalanche replacing the midgate. I built a box for them that was 4.5 sq ft with 16cu in port area and I’m not impressed. Any help would be greatly appreciated.