if you already made your box then you need to:would the port displacement for one 4" aero that is 20.5" long be .149 i was wondering if my math was right and another thing do i add that to my box and then do it again to figure out how long they need to be.idk im kinda confused my box is. 4.59 with sub displacement and i want 4 4" aeros tuned to 38 any help