Epoxy resin has superior adhesive qualities over poly, so I always use it for fabrication and repairs on our boats.
Note that when filling a hole you always need to chamfer that edge back at a 12 to 1 ratio, per the instructions in the excellent manuals you can d/l from West.
Epoxy by the Leading Epoxy Manufacturer | WEST SYSTEM Epoxy
Fiberglass Boat Repair and Restoration
If you are working on an Ericson, just post up your questions to hundreds of other E-27 owners over at the main site, EricsonYachts.org: The Starting Point on Ericson Yachts!