The panel bond will outperform 4 rivets. The rivets would be subjected to far more stress on their shanks than the panel bonded part. Compare the entire surface area of the brace boned to the fender. I unrstandunderstand Orbs that you are unfamiliar with the stuff, and have a reasonable level of skepticism over it. But as others have said, it is unreal strong.
True, once applied and the parts squished together, you can bury them for all eternity. Maybe not the best product for this application if the OP ever wants to service the pieces separately. But as for strength in application, nothing better.
And "wind" will be channeled along the underside of the fender somewhat anyway. Needs to be strong, sure, but panel bond will do it. Have seen aluminum hoods on hot rods attached to steel subframes and withstand 100+ drives. And that's a LOT more surface area to deal with the wind stress.