Last night, I had the idea of making a fluting tool from a block of steel and using my Knipex pliers to form the flute. Those Knipex pliers have great mechanical advantage, so it should be possible to exercise fine control of how deep I make the flutes. I started by cutting flat sides on this piece of steel rod.

Ground the end square.

Used the angle grinder to grind out an inclined trough in the middle of one of the flats.

More cutting, grinding, sanding, and polishing later, I had the little two lobe form tool on the left to use in conjunction with a bit of 3/16" rod to form flutes. The trough in the form tool is .250 wide, so it should have just enough room for the .187 rod and twice the .032 material thickness.

Here's the setup just before forming a flute.

...and after.

Okay, that looks good. Plenty of curvature. Of course, I can't space the flutes quite this closely or there will be no room for rivets.

As mentioned, plenty of curvature.

I fluted another piece of material. This time, it's a rasonably good match for the actual curvature of the canopy skin.

With this test part positioned to match the canopy skin, then held in place with magnets to the sub panel, I removed the canopy frame and traced the top edge of the sub panel on the back of this flange. It looks like I need to trim the top edge some more so that it lies more evenly just below the bend of this part.

Used a washer to trace a cut line on the sub panel that is 3/16" below the surface of the canopy skin. I'll trim this tomorrow.