Hinge off- holes in decent shape. The old hinge is trashed from sanding.
I don't care that the old hinge is trashed. Here I have a cheapie aluminum angle from Menards. It has a square inside corner. I butted the hinge into that corner and transferred holes.
Then I popped the hinge off, got a .040" shim, and a new piece of hinge. The holes are transferred from the angle to the new hinge.
Here is before and after. I am going to rivet the hinge back onto the flap with a handful of aluminum rivets tomorrow for a fit check. If it is good I'll drill them back out and rivet it for keeps.
To do things right the first time is easy. To fix a screwup takes true skill.