You can make a 28" port in a 20"-whatever length box. I made a 24" port in a 20" box...just make a right angle in the corner and run the port down the backside, its easy.Originally posted by v8s10 HEY MAN.. LOOK AT THE V8S10 THREAD!! YOU MISCALCULATED BUDDY.. AT LEAST AS FAR AS I CAN SEE.. need to fix it so i can finish this box!!!