Satisfied with the cut line, I flipped the canopy back over and unclamped the sides. I tried a cut with the frame in the canopy, thinking the extra stability would help, but this was more trouble than it was worth. Removed the frame and finished the cut with the Van's cutoff wheel. Used the flap wheel with 60 grit for final adjustments, clamped a piece of aluminum to side for reference and to prevent sanding off too much material. Finished edge with multitool and various grits of sandpaper as before.