Install the L angles stiffeners to the Side Skin. Start at the first vertical line of predrilled holes aft of the second window. The vertical L angles overlap the rivet lines for the Longerons. The diagonal L angles don’t overlap any other stiffeners.
Install the Longeron to the TOP of the Side Skin. Position the Longeron with the edge of the Side Skin against the lip on the Longeron at the start of the radius. The vertical L angles should overlap on top of the Longeron. With a #40 drill bit, back drill through the Side Skin into the Longeron and Cleco as the holes are drilled. With a #30 drill bit, expand the holes and Cleco. With a #20 drill bit, expand the holes from the vertical L angle aft of the first window forward.
Cleco the Forward H.T. Frame and Rear H.T. Frame to the Bottom Skins. Expand the holes with a #20 drill bit and Cleco. L angles are shown Clecoed to the H.T. Frames in the photo above, this is done in a later step. Deburr the H.T. Frames and Bottom Skins, Cleco, and rivet the H.T. Frames to the Bottom Skins.