I have long been under the impression that when bonding new fiberglass to old, the bond is purely mechanical and will not hold up long term. When bonding new components (such as spoilers, ground effects, wheel tubs, etc) to an already cured body, what is the best method for creating a bond that will last long term without cracking or breaking?

Mind you, I've yet to build a car or do major fiberglass repairs. My experience thus far has been limited to duckboat building (where everything was laid up wet), compound bow limb repair (uh, yes I did!), and some other miscellaneous projects. The largest job I've ever done (besides a duckboat) was to repair the bucket on an electrical bucket truck. In that instance, I used epoxy resin with cloth to re-attach a control panel cover to the bucket. I haven't seen that truck in about six years so I hope that repair is still holding up.

Anyway, I would like to hear some thoughts from some much more experienced fiberglass craftsman here.