I am done preparing the tanks, but don't have any proseal so while I wait for it to arrive from Van's I prepared the Joint Plate T-423. There is not much about these in the mfg plans, but lots of info on other builders websites. First I decided it was important for the platenuts to be centered on the dimple and hole. So I cut a short screw and used it to screw in a platenut for drilling, countersinking and riveting. But first I dimpled skin rivet holes with #40 and the screw holes with #8. Then I screwed on the plate nut and drilled the rivet holes. I have the new 1097 rivets which have a 3/32 shaft but a very small head. So rather than dimple the rivet holes I countersunk them. It didn't take much. About 12 turns with the deburr tool or countersink bit.
Cut off screw and platenut for drilling and riveting
Drilling rivet holes with platenut securely centered