Kristi, et al,
When the fiberglass TT body becomes stressed during an emergency manuever or a rough road or even a good sized pot-hole where is the "weak link"? With aluminum pop-rivets, the fiberglass generally proves stronger and the repair only requires replacing the rivet. Using a bolt will require a much more involved repair of the fiberglass, particularly if the cracks are deeper than surface stress cracks.
Stress tests of plastic rivets used with fiberglass will need to be published to convince me to change. The issue of UV deterioration might be addressed by including an ingredient in the plastic formula which would counteract the problem (possibly lamp-black). Painting
or caulking the head of the rivet could also be the answer and may even be a requirement to prevent moisture from seeping in along the stem.
In my youth, I always attempted to make things stronger, assuming stronger was better. As I've added a few years I've discovered that axiom isn't necessarily true. Among many other examples, automobiles are designed with "crush zones". Not for the purpose of making the manufacturers rich by boosting the number of parts required for repair, but to protect the occupants so they
don't have to be repaired.
It became smarter for the car to be the "weak-link" than the human being riding inside.
Please consider all
the ramifications of your decisions before starting in a direction which may not allow you to go back to the starting point. Come to think of it, that advice is appropriate for nearly all aspects of one's life.
& Ann K.