I am looking at using a box off of the free box design but I am going to change it a little. I was going to do away with the center support and use a 8"(7.75 id) aero port rather than the slot ports. It will be 16" long. Will with effect the box at all? I think that my tunning will be about 35hz. I attatched the pic of the box. Any and all hep will be great.