I have 1 PSI P1 15" sub in a 4.5 cubic foot ported enclosure. I have a 6" diameter aero port that is 10.5" long. My box is a 6 sided wedge design and we are trying to figure out where to place the port. I have a 2010 Hyundai Accent Hatchback and my box is in the very back. Here are my 2 options. Option 1: Port on top of box next to the sub. Option 2: Port in front of the box on the angle. If the port is placed in front it will be a few inches from the back of the seat with the seat up. If it's placed on top it will always be in open space. I would rather it in the front so i can blow more air towards the passengers but i dont want the seat to interfere with the sound quality if i ever need to use the back seat.

I would say to just test it man. Cut two holes, then find a way to block one hole while trying out the other. The only real way to find out. 

Cut two square holes, one on each face and make two slightly larger wood plates. Mount a port in each plate of equal length, and block the opposite hole for testing. Whichever configuration you like, mount a plexi window over the other. If it's double baffled, you can do plexi, or just plug it with wood.