Moving back to the rudder, I finally countersunk the trailing edge wedge. I used the Cleaveland Tool wedge jig to hold the material square to the countersink cutter, and made sure to support the balance of the material.
I was able to complete the countersink easily, and was happy with the quality of the work accomplished. I then trial fit the wedge between the skins with the angle stock jig I created to practice the layup required when I proseal the wedge into place between the rudder skins.