The fabric back is by mom. Prints from the frame are below. Be sure to note where not to glue. If you plan to heat bend the PVC stringer that goes behind your back, add minimal temperature...and be careful - fumes from PVC are very dangerous.This bent piece is about 14.5 inches long, but you will need to size it on the fly as a last step in you construction. An alternate method is to use a flexible pipe for the curved section.
I simplified the drawing from my earlier posts. Click on the picture to get a larger view.