I also spent quite a bit of time on the end panels. It was a little stressful but I got the chamfers all cut, the curved one was the scariest. I was worried about it being wavy because neither the jig nor panel was sanded smooth. It just came to me one day to use one to sand the other and vice versa. I stuck some sand paper to the curved edge of the panel and sanded the jig. Once the jig was nice and smooth (and free of the waves that a spindle sanded will leave when you're new at it) I used it to sand the panels. Another nice thing about this method is that the curves end up being identical. Here's the jig i used per the specs in the plans.
As I said, I was really nervous about this but It couldn't have worked better. Everything slid smoothly and I just snuck up on the thickness. Doing the other 3 sides was a breeze after this. The next, and time consuming, step was to fit the panels nicely into the frames. I had to lots of fine tuning with my smoothing plane and sandpaper on the bevels but all is well. I'm very happy I decided to go with the raised panels for then ends. They look so much better than a solid panel.
Besides the end supports, the next step is more work on the sides. I have to cut all the little filler pieces to go in the groves between the slats.