The seat bottoms are merely cushions tht rest on a canvas sling glued to the front and rear spar carry-through. It laces up with heavy chord in the front. Airtex carries the sling. The backs are welded tube affairs. I'll see if I can find a drawing, but there's nothing like having one to use as a template for making new ones. I'd try the "Fly Market" area of the BCC website or contact Harvey Leydecker in McCalla, AL. I seem to remember her had a seat back frame last time I was down there. His number is 205- 477-6342.