Started countersinkin of platenuts using a fabricated alignment based on a technique I found on the internet. Found this to be quite cumbersome. Re-read the Van's builder manual and determined that I just needed to rivet the platenuts to the spar first, then, countersink the screw holes for the tank skins. The pilot countersink will use the platenut screw hole to align the countersink. Much easier than the adapter method I started with.
Used #40 bit to drill platenut rivet holes, deburred, countersunk and then primed the areas where anodizing was removed by countersinking.
Riveted the platenuts using AN426AD3-4 rivets and the 4" No-Hole yoke in the Main Squeeze squeezer.