After disassembling all the rear ribs and spar bulkhead, I deburred all the ribs and the newly drilled holes in the spar. I also dimpled the rear outboard seat ribs per the instructions. Then I assembled the rear spar to the footwell ribs and riveted the outboard ribs per the instructions (with flush rivets to fit under the bulkhead parts). Next, I assembled the bulkhead parts and riveted them. Finally, I assembeld the rear seat ribs that had seat belt anchors and riveted the anchor parts together. I finished the day by clecoing the ribs in place, but I need to find out if the outboard footwell ribs get dimpled before riveting, so I may have to remove them before continuing.