Matchdrilled the trim tab horn to the trim tab skin: First drilled the inboard 3 holes to #40. Then drilled the outboard 4 holes also to #40. Resulted in elongated holes in the skin (where the horn with the reinforced steel sheet didn't match the pre-punched holes). Deburred and dimpled all holes to #40. On the elongated holes, biased the dimpling to the side that matched the holes in the horn. Enlargened the elongated, dimpled holes to #30 for NAS1097 rivets. The elongated holes all but vanished. The result looks fine. Matchdrilled and deburred the trim tab skin to the spar.
