2 15s 8.625 gross aero port? i can get some 6 " pvc for free. from my step dads work and will use that for the port. my question is should i use 2 3 or 4 6 inch ports? desired tuning of 33 will be daily box. want to have 7 cubes net. any suggestions? will be double baffled with external dimensions of 38x 18x 27 ive always done slot ports and want to play around with round for this build. thanks for advice.