Need help with an enclosure design for 4 Skar ZVX 8 D2

[Twillis6]

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 2004 Chevy Avalanche replacing the midgate. I built a box for them that was 4.5 sq ft with 16cu in port area tuned to 34hz and it looks great but I’m not impressed with the output. After just 2 days of playing them I blew a sub and I’m assuming that it had something to do with the box and I know that I was clipping but this time I’m going to get my gains set at the local shop until I can afford a dd1. It didn’t sound bad but I know that these should be much louder.Any help would be greatly appreciated.