trk2loud

Hey guys I need help with a port tuning for my brother's setup lol, it's going into an old bettle so...he's crazy. Ok he has two 15" RE HC's running at 1600W RMS all the time. I want to make a box (EXTERNAL DIMENSIONS = 48"L 18"D 26"T = 10.22 cu ft.) I don't know what to port it at though...He wants it to just make his car shake like crazy and to be extremly loud when turned up. What do your suggest for porting? He'll run circle, slot, or rectangle port it doesn't matter. Let me know Thanks, any suggestions will help!