k, i can fit a 5" port for my box.. its either 5"x8.35" or 4"x4.76". With the 4" diameter i think it might not be big enough, but the 5" might be a little to big. My box design is kinda weired so i will need to bend it.. would you say the best way is to figure out the total area in litres of the 5" wide port then just make the necesary bends and figure it out like that? Thanks.