Let's try this. You should know that I removed the seat but did not remove the seat base. This made some of the measurements difficult and I had to take inside measurements some times and outside measurements other times. The metal of the riser is 18 gauge. All numbers are in inches. I don't really know how to measure curves to I approximated the straight portions. Specifically, the front edge of the top view; the 9" is the straight part, the 18" is also the straight part. The curve is not critical so it doesn't really matter. Also I forgot to include measurements of the small curved area seen on the side view. So, the curve is within 2 1/4 inch of the back and the curve is 4 inches wide.
I probably have confused you beyond belief but feel free to respond here or private message me and I will try to help.
