After putting painter's tape on the metal surfaces of the brake (since the polished skins will make contact with the metal of the brake), I bent the elevator skin.
I used some scrap aluminum to make angle guages to get the angles right. You don't want to bend any of these angles too far. Thin aluminum doesn't do well being bent back and forth if you bend it too far.
After getting everything bent, I needed to use a piece of 1x and a lot of body weight (and some key bouncing) to get the acute angle to close up as much as I could. What you see in the 3rd photo is as far as I could get it, but it looked fine when I closed it around a rib; plenty flat enough.
Using an angle guage made from scrap alum to get the angles right
Using a piece of lumber to bend the skin a little further.
And finally using another piece of lumber, with my body weight, to bend it further still.