My recollection is that the back seat cushion is attached to the seat frame which uses maybe something like the old leather (similar to that used in some of the open car top frames) to staple or tack those portions of the seat back upholstery in place on the sides - the top portion is tacked or stapled into the wooden seat rail that goes across the back of the seat frame, and the bottom ties into the seat cushion as best as I recall. The bottom seat springs are tacked to the wooden seat frame using clips, and from there the fabric/material attaches to this wooden seat frame as well. There is a rear cardboard panel that screws into the back of the seat frame and is visible from the rumble seat. Attaching the seat back to the frame is a most challenging matter. Please let me know if there might be anything further that I can offer. I've never had much luck posting photos, but I can perhaps send you some photos of our 68C upholster via e-mail if you think that might prove helpful. Good luck with your project.