After I stuffed the seat-backs with foam, I glued in the seat-back panels. Once the epoxy had cured, I trimmed the top of the panels with a (modified) tenon-saw to 1/8″. Some time ago I removed the back (aka spline) of the saw – it is only the blade and the handle. This blade is somewhat flexible, sharp and has a thin kerf. Without the back I can make long cuts in plywood. For the last bit of the tops of the panels I used some #80 in the ROS.
The two small panels resting across the boat are the seat-back tops with their first coat of epoxy.
I also added two more of the curved cleats in the cabin.