WE had the fender flares attached that way, ran into trouble with it adhering well in a few spots, probably due to the ceramic coat we had applied. A bit of abrasion with a magic eraser and good cleaning with alcohol fixed it.
We had trouble with the flare adhering, finally figured out that it was the clear coat we had done previously. Our detailer suggested a light abrasive wipe where the adhesive meets the body,.The one spot is still loose... has anyone used super glue?
Our son, a professional detailer specializing in ceramic coat, did our truck right after we bought it last year. It still looks fabulous. You already spent big on that sexy truck, spend a few more bucks to keep it looking good, and protect the paint.