a rough scuff on both surfaces, 2 part epoxy applied to both surfaces, drill-screwed, 3 inches on center, to fender and let to cure for a week before driving.
removed screws after 3? months.
2 years later, zero cracks,zero imperfections and that's without body stiffening and a V8 car. so you know that body is flexing.
i would definitely do it again.