I'm also going to be building an enclosure exactly like this. Only item I ran into while designing the port was the width/height ratio on the portion of the port along the back wall. The steeper the angle, the taller the height became. It took quite a bit of trial and error to finally get a design that didn't cause that portion of the port to have a ratio close to 1:8.
A pair of Rockford Fosgate Series 1 12's in an Obcon bandpass box, pushed with a Punch 100. 1994 or so? First time I understood what the fuss was about DJ Magic Mike CD's.