Went easy once I figured out the secret! 1st....be sure to see ANOR for correct location. 2nd ....you will not be able to drill the holes from inside the FWD spar...the holes are too close to the web of the spar. Once you drill out the rivet from the bottom of the wing (outside), then mount the nutplate to the outside with a bolt then drill #40 holes from outside the wing. Move the nutplate to inside spar as shown in figure and mount. I used -6 rivets but -7 would work best.