This is a problem area with many fibreglass trailers. I have four Trilliums, and each of them will require major work on the hinges. The design is flawed. That is if you call something flawed, that has lasted 30 years of rough service.
There are many possible approaches to the repair. They range from gluing some wood chips into the holes, then screwing in the screws before the glue sets, to something like this:
http://www.fiberglassrv.com/forums/f...air-47624.html
Either way, probably not the hinges.