The flange for the deluxe locking fuel caps is milled to match the curve of the upper wing surface. This means it is thicker in the center than on the forward and aft ends. The standard rivet callout in the plans is for a flange that is bent to shape and the same thickness all the way around. I used the formula 1.5D + G to calculate the correct rivet length.
I used a micrometer to measure the flange thickness at each hole location around the flange. I added .032 for the skin thickness and .025 for the clip on the forward most rivet. Then added 1.5 times the rivet diameter. I compared my results to another builder's log and agreed with his callouts for each location.
The forward hole with the clip is a 5; moving around the flange the rivets are: 4.5; 5; 5; 4.5; aft hole is 4; then 4.5; 5; 5; 4.5
