Step 6: Rivet the F-1079 Aft Bottom Skin to the F-1011 and F012 Bulkheads, and to the F-1073 Left Side Skin. Step 3: Rivet the Left Side Skin to the Stiffeners, Frames, and Bulkheads from aft to forward. Out of sequence but seemed to work ok. I did notice a very slight raised area at the center of the F-1079 Aft Bottom Skin and the Left Side Skin. This raised area is slight, on the order of magnitude of 1/16 in from square and was not noticeable until I saw a slight distortion in reflected images in the shiny aluminum. I'm painting so this should not be seen under the Hz Stab.