After sleeping on the problem, I concluded that it was worth a shot at rebending the flange. Since this part of the skin is hidden after assembly, I realized my task was to increase the flange width to shorten the back web, meaning that all distortion of the aluminum would be inside the closed skin. I opened the flange as far as I could by flange pliers, then placed it on the edge of the table and hammered it down with a rubber mallet. The last step was to place a block along the crease and hammer it out with dead blow hammer. Then I measured the correct distance from the crease between the bottom and the back (77mm) and re-bent the part, this time placing the flange in the bending brake. With minor tweaking, the part met specs, so I'm good to go.
