I tried a couple flush rivets (AN426AD4-8) as defined in the instructions, but it looked too short. So when I ordered more flush rivets I also ordered some 4-9 size. These I checked the length after installing, but prior to squeeze and it was right in line with the recommendation (1.5 x rivet shank diameter). I noted the change in the plans and completed the rest of the riveting with the AN426AD4-9 size. Overall I'm happy with the results.
Stated riveting the center section with the flush rivets
AN426AD4-9 turned out to be a better length
Results turned out well with the 4-9 length rivets
