The biggest trick is to make sure the fiberglass is prepped and cleaned extremely well. Epoxy doesn't stick well to polyester and polyester doesn't stick well to epoxy. That said it is mechanical bond we are looking for. Sand your glue surfaces with 80 grit paper (any coarser doesn't really cut well, it just glides over the surface too much) or 100grit. Clean it extremely well. Many people use acetone, I prefer a good quality virgin gun wash or laquer thinner. The truth is if you don't prep it well even polyester doesn't like to stick to polyester or epoxy to epoxy. If you have concerns about the hysol you can use an automotive product known as panel bond. 3m makes it, so does proform. It is a thixotropic polyester adhesive designed for gluing new panels into cars in the bodywork industry.

on major structural formers like the fan and wing mount even with hysol in there I personally would still sand and reinforce with fiberglass cloth and resin too. It helps spread out the load over a bigger area.