If you are going to "fix" your fiberglass fairings, do it right the first time....spend $20 on a fiberglass repair kit and read the instructions. Don't slap 2lbs of bondo over the crack and expect it to hold. Then when that fails, don't slather a 1/4" layer of silicone caulking all over the inside of the fairing. And finally when that doesn't hold, don't get out pieces of aluminum and pop rivets as a last resort. All that shit does is make more work to repair it correctly.
/rant
If you are actually interested in fiberglass repair and the rant didn't fulfill your needs, here's what I've posted previously: