Riveted the bottom access plate platenuts on after drilling to #40 and countersinking for the AN 426 rivets.
Then using Van's suggestion, I countersunk the tank platenut on the spar flange for the #8 screw. I cut off a #8 screw to fit into the platenut easily to gauge the depth of the countersink.
Countersunk the holes with the #30 countersink.
Countersunk the holes on the access plate part of the flange with the #40 countersink. Worked great. Spot primed everything.
Began construction of the tie down wedge by trimming. Drilling the top right hole per the plans and tapping the bottom end 3/8ths, 16, 1 inch.