Just scratch through the paint where the brackets go. Use 3m 5200...a liberal puddle, place your panel, after it dries cover the top of the bracket and over the edges cover your original puddle. Properly cured...follow directions it will never move. Use the quick set version.
Try a test piece on something first, it also comes in toothpaste tube size...if skeptical. I put a rivet through each of my brackets 12 years ago...waste of time.
https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Marine-Adhesive-Sealant-5200-Fast-Cure/?N=5002385+3293241048&rt=rud
