Making the sidewall profile templates out of 3/8″ plywood. I made 2 section templates for both the of the wall as well as the outside. Each template needed one and a half sheets as they are just over 9′ long. I used a 2 inch grid and drew the curves connecting the marks with a thin piece of scrap.
I marked the profile lines with a sharpie.
A jigsaw was used to cut the profile. The lines were drawn to the outside edge of the line so the saw could cut up against the inside edge and get a very exact line.
I used a shureform and a sander to smooth the edges a bit. Since the black line was marked to the outside of the cut, it allowed me to easily see if I needed to take extra material off with the hand plane. Make sure you keep the edges 90 degrees to the surface or your template or you will have difficulty later when you transfer the template to the wood.