Right now I have my Rockford 15" T1 sitting in a 2.75 cu. ft. box tuned to 32 hz running off a Hifonics BXi1206D. I'm looking to make a box tuned slightly higher for a half-decent score at local SPL competitions (approx 35 hz or so?). I've looked around and most people are sticking their 15" subs in 3-4 cubic foot boxes. Am I giving this sub too little room? Should I go for around 3.5 cubic feet? Please help me out here! Advice is greatly appreciated.