Today I attached the platenuts for the W-822PP access plate. I then countersunk the holes for the #6 screws that attach the access plate to the spar. I had to sink them deeper than I thought I would so that the access plate would sit flush. This made me wonder if I had countersunk the holes for the tank attach screws deep enough. I fabricated a test piece of aluminum sheet the same thickness as the tank skin and sure enough, they needed to be deeper. I went back and sunk those a little deeper.
I moved on and attached the K1000-4 center section attach platenuts to the forward side of the spar and countersunk their attach holes. I then spot primed all of the holes where annodizing was removed from the spar.
I got a reply from Van's about the spars being mislabeled. They said that it looks like I am correct in that they are labeled backwards but it shouldn't matter in the long run. Thankfully!