This was not easy. I found out that I have to drill out the rivets from the angle (PArt 10SF) that fastens the floor to the side wall and move it back to leave room for Part 10S lip.Since I had a lot of room on the angle I decided to drill new rivet holes and once re-riveted use the screw hole to drill the Part 10S hole. I also put a rivet into the old outer rivet hole between the floor and Part 10R (counter sunk). It was very difficult to get a good fit at the overlap between the sidewall, Part 10S and Part 10SF. At the end it look really good.