Trimmed the top edge of the sub panel to provide even clearance to the canopy skin.

I also made another attempt to make this top flange by forming the curvature with a whole slew of deep flutes. The curvature is pretty good, but I'm not sure this is going to be good enough. The "flat" surface is somewhat distorted from all the flutes. Also, there is very little space between the flutes to permit riveting to the sub panel. Frustrating.