Pilot drilled the top of the left wing middle skin.
Turned the wing over and pilot drilled the bottom of the middle skin. Then updrilled to 1/8" from the spar aft. Updrilled the leading edge with #32 drill. These need to be dimpled which enlarges the hole slightly. Depending on how much expansion there is, they may need a final updrill to 1/8" or #30 drill to clean up the holes.
Turned the skin over again and installed the outboard skin and updrilled with #40 where needed.
When installing the skins, I cleco'd the trailing edge of the top skin and wrapped the skin around the wing and installed some cleco's on the bottom trailing edge. This ensured the wing was square to the aft spar and substructure. I then finished pilot drilling the top skin before turning the wing over to pilot drill the bottom side. All pilot drilling was done from the trailing edge moving forward per the General Construction Order noted on the print.
Still need to pilot drill the bottom of the outboard skin and pilot drill the aileron hinge.