I started by match drilling to 3/32 the aft half of the F-623 right corner rib to the bottom skin, then installed and finished drilling the F-623 fore and aft clips on both corner ribs. I then clecoed the bottom aft corner of both F-770 side skins in their final orientation between the corner rib and center bottom skin in preparation for later final drilling.
I then clamped the longerons to forward and aft side skins and drilled both longerons from the aft end forward as far as the F-706 bulkhead (photo 1).