check over my design for a single xd8

Is there something your thinking is wrong?

You are right about the specs for the baffle being the same size as the rear. That can't be right with the port up front. Maybe that software just doesn't account for it.

I usually measure then sketch a drawing of how I want the box assembled and figure out the volume. Then I calculate the port using WinIsd and finally model the whole thing in sketchup.

You 'might' want to up your "port area per foot" a little bit. This might require you making the box slightly larger though. Someone please correct me if wrong, but I believe its a general rule that you want between 14-16 sq in per net cubic ft. The first box I built for my SA12 had 12 sq in of port per cube and my newest one has 15.5 per cube and I definitely noticed a difference in output.