Bonding fiberglass to steel

[BigBlockOlds]

What product out there is the best at bonding fiberglass to steel and NOT developing cracks later on in the paint or having the fiberglass pull away?

I have as set of fiberglass fender flares that I want to mold into the body sheet metal. Obviously the will be held in place by screws in the wheel well lip but where they meet the fenders and quarter panels I would like to have them molded in.



Or, would I be better off just making them bolt-on with hidden fasteners?

Any ideas. procedures or product suggestions would be great.

Thanks,