Right Rear Spar riveted to Right Bottom Skin per Step 4 & 5 - with some exceptions. Then Sect 9-18, Finished Right Bottom Skin via back riveting Ribs.
Sect 9-19, Step 1 Left Bottom Skin - 5 Ribs, since 6th is part of Trim Reinforcement Doubler. Riveted Trim Access Reinforcement & Doubler Brace while adding final 2 Nutplates. Note: I add the machine screw during riveting to insure alignment (these are flush, so no interference, etc).
Step 2 Back Riveted 6 Ribs to Right Top Skin. Started Step 3 - cleco'd LH Top & Bottom Skins with Ribs and Rear Spar so ready tomorrow to blind rivet top and bottom together. It's beginning to look like an elevator!