I have done something similar to Bernhard for a Vincent that was for sale. I had a roll of 3" wide fiberglass cloth. I wet it with epoxy and ran it under the reinforcement strip for the center and also spots where the stay bolt holes were. I did this to a new mud guard, so it was clean and undrilled. I used two layers, but spread them a little so they overlapped where the bolt holes were. When it cured, I drilled the holes and mounted the mudguard with the reinforcements like normal.
I don't know how well it worked. I felt that even if the epoxy let go of the aluminum that the fiberglass would stay put as an additional fiberglass reinforcement sandwiched between the mudguard and the reinforcement, spreading the shock from the vibration and extending the life of the mudguard.
David