Removed plastic strips from around stiffener holes in skin. Back-riveted stiffeners to skin. Unlike right elevator, all dimpled stiffener holes were lightly countersunk (from outside of skin) with deburring bit before rivets were installed (like on HS). Results look great. Fluted E-603 and E-604 tip ribs. Aligned, clamped, drilled and clecoed them together. This went very fast, thanks to previous experience on right elevator.