I flipped the Center Fuselage Assembly upright and clecoed in the seat and baggage skins. I then drilled the holes to final size. While doing so, I immediately saw that I had made a mistake by previously installing the platenuts to the center baggage area ribs. The platenuts are to be installed through the skins and ribs together. I called Joe and he said to build on. I will install the platenuts correctly on the center ribs in the seat section. I fit the F-715 Outer Seat Ribs and drilled them to the F-704 Bulkhead. I then drilled them to the bottom skin, being careful to line up my previously drawn center line with the holes in the skin. I used a piece of .032 scrap aluminum to position the upper edge and drilled them using the holes in the skins.