My replacement end caps arrived from Anti-splat. Before when installing, I didn't make sure that these were level to the plane....They were clamped tight to the gusset and the longeron, but that didn't mean they were level across the airframe.
This time, I installed the endcaps and made certain that they were set parallel and perpendicular to the centerline of the fuselage. I used a straightedge and spent a lot of time measuring and marking.
Once I was satisfied with that placement, I placed a level across the plane and made certain that the end caps and gusset plate are level (perfectly horizontal). Once satisfied, I used the same drilling technique and template that I used before and finished all of the mounting holes. Note the blue lines showing horizontal level on the front of the end cap and the line on top of the end cap that aligns with the edge of the gusset plate.