Rivet the R/H wing spar extension to the main spar with 15 A5 rivets and 6 A6 rivets. Drilled the 5 holes on each of the R/H wing rear ribs 1,5,6,7,8,9, where they attach to the spar, to #21 holes. They had pilot holes in them so I used a tapered reamer to get a perfect hole.