Verified alignment of aft fuselage assembly and Pilot / updrilled bottom skin to bottom longerons. Removed bottom skin and deburred holes in the skin and longerons. Started assembly of the tail skid to the lower vertical fin spar along with the lower aft & lower forward mount angles. Keeping everything square pilot/updrilled required holes. Disassembled, deburred, and cleco'd back together. Flipped aft fuselage assembly over and following detail B (Manual Ref. SNX-F21)-clamped, drilled, updrilled, disassembled, deburred, cleaned, reassembled and finally riveted top tail cone box assembly. The bottom of the tail cone box assembly will be riveted on a later assembly.