16-2: Step 2: Final-Drill #40 holes of top skins. Step 3: Final-Drill #19 screw holes for nutplates. Dimpled aft most screw hole. Machine countersunk rivet holes commont to wing walk doublers. Step 4: Disassembled all parts clecoed (sore hands). Step 5: Began sanding the mating edge of the inner top skin to blend joint between two skins. I'm finding I am having better control of the blend depth by hand with a sanding block than with the electric sander I started with. May take longer but I think I'll get a better blend line (this is going to take some time). Have reduced the edge from .035 to .028 so far. Plan to go to .020 at the edge. Calipers is difficult to judge these kind of gradual measurement so I will probably get a micrometer to finish up.