Marked hinge rivet line 8mm from top edge of trim tab. Marked 23 hole locations along the line which came out at the 40mm pitch specifed on drawing. Noted that the left elevator rib line does NOT end on one of the hinge rivets.
Clamped trim tab between steel bar and strip of wood then applied clamp force to bring the top edge and radius of inside flange up to the same vertical plane. Pilot drilled holes with a depth stop on the drill bit to ensure it didn't get into the web or bottom of the tab.