Working on the passenger side side skirt. Just like on the pilot side, I used the trick with the two aluminum scrap pieces to mark the height of the cut line above the rectangular frame bow line.
You can see a reference line in the image below and then the small black line near the edge that indicates the ideal depth. Used the hand-belt sander to grind away the excess material and sanded it down to 600 grit.

After some repetition of trial and more sanding, I got the distance perfect and drilled through the top line.

Close up shot of the alignment view from above and the front or the frame.

Skirt removed reveals the good edge distance on the canopy edge and nice smooth holes.Those plexi drills are really fantastic.

Next I started working on the skirt brace. Cutting lightning holes and drilling the upper and lower holes

Job done.