well i built a box and it was too big. (ITS PORTED and thats whats complicating things)

what im trying to do is shorten it down enough that i can get it out of the trunk without taking it apart and therefore once that is accomplished it can be glued airtight unlike it is now.

i plan to leave the height 13.5" (since the sub is a 12") and width 25"
therefore the port hole will be the same size and i will cut down on box size reducing the depth. i need to kno if its possible to change the length or design of the boards on the inside of the port (the boards that make up the L) to match up with the original tuning frequency?