Hey guys. I'm new to the car audio world and was thinking of running two 15" DC level 4's off of a DC 3.5k amp. I have no idea how to design boxes but know that it should be tuned to around 33hz for sq and that each sub recommends 3.25 cubes. I was thinking both subs and port up but really have no idea what is best. Max dimensions for box are: Height-20", Width-39.5", and Depth-31.5". Box designs would be greatly appreciated