I've personally found that polyester resin isn't a very good glue except when bonding other polyester resin parts together, and is also best used in conjunction with glass tape reinforcement as polyester resin alone is rather brittle. I would suggest using a good acrylic adhesive (best), or more of the slow cure epoxy as this is tougher and will deal with the wide variation in expansion rates between PVC and the glass fibre hull which will stress those areas.
Rough the PVC parts up well where the bonds will be, as the adhesion will be mechanical not chemical.