I used a hole finder to drill the holes that will attach the fiberglass skirt to the canopy:
Then I spent some time laying out reference lines (perpendicular to the rivet line) at intervals of one inch along the entire skirt. These I used to measure and mark the true cut lines for the front and rear edges. Unfortunately I don't seem to have taken a photo of the skirt after all the trimming and sanding, but suffice to say it fits well and the edges are a lot nicer than this "before" shot.
My resupply order from ACS arrived, so I mixed up a big batch of epoxy and filler and applied it to the surface of the skirt, while it was being held in place with a single cleco on each side just to hold the shape.
I'll have to do a lot more filling (and sanding) before it's through – this is just a reconnaissance mission to fill the cloth weave and help identify low spots that need more filler.