Actually PU adhesive would probably be fine, in conjunction with rivets, being non structural. 2 pack panel glue is more for structural areas.I have a couple of similar repairs to undertake on my replacement station wagon tub. My plan was to use tigerseal (or sikaflex, i am not brand loyal!) to glue the repair plate in place along with some rivets. I am not trying to achieve a perfect finish so am not trying to make invisible repairs. I have a large sheets of 3mm ali to cut the relevant parts from, but have the bottom edge simialr to you, and some parts of the wheels box to do.