I was messing with WINISD and i was coming up with some pretty outragous numbers. I want to run 2 12"s off of my HCCA-D5000. Went i looked up the size for a ported box (max flat response with at -3 at 30db minimum) it recommended 9.5 cubes, which i dont really think i can swing. I got pretty close at 4.4 cubic feet but to tune to 21hz it calls for a 400+in port length. Help!