For the port, I built an actual little box that is 8.5" long. The double baffle will add another 1.5" of thickness to give me the full 10" port.
Once the boxes were built, I glued them to the baffle.
A nice tip in the forums about the port hole in the baffle is to do a rough cut first, and then use a flush trim bit on the router to get it nice and smooth. It works great and is an (almost) idiot proof way to do this, and is now my new favorite tool+bit combo that I own.
See the front... pencil marks is where the hole should be cut.
Through the back of the port... you can see the overlap that the bit will cut off.
And 20 seconds of using the flush trim bit. You can see my pencil lines were off a little bit. That would have been a pain to try and correct had I cut it where I marked. And not only that, but I've got rounded corners for the port. That looks cool.