Used a chart and homemade guide to get the necessary 5 degree angle to drill perpendicular to the chord line as per instructions.
A rough drawing of the trailing edge configuration.
Home drill guide in operation.
Drilling in progress.
This close-up shows the trimmed trailing edge. A bit more rounding is needed to smooth the AEX piece. I intend using ProSeal (or equivalent) on the trailing edge, so hopefully some of the empty space will get filled with this material.