Making sure the the pitot mast plate was held in place correctly, the support bracket rivet holes were drilled and the rib match-drilled. The four #40 holes in the mast plate had to be countersunk by hand because of clearance issues to fit the skin dimples. Clecoed the support plate to the rib, taped the front edge of the mast plate to the spar, slipped the bottom skin over the mast and test fit the assembly and bottom skin to the wing.