Matt---I'm not sure what you mean by "fiberglass putty". Do you mean polyester bodyfill? For bonding purposes, liquid resin works better. Bodyfill will work too, but the bond is nowhere near as strong. Uncle Bob is right about epoxy resin being 4 times stronger, but methinks it costs about 4 times as much, too. You should be able to go to a NAPA dealer and buy a pint of resin and a small squeeze tube of liquid hardner.