I've always heard Vinyl Ester resin is superior to Poly Ester resin for boat building. You might want to consider that because from the prices I'm seeing West System Epoxy is around $300 for 5 gallons, poly ester resin is about $150 and vinyl ester resin is about $170. Big difference between epoxy and the others, not so much between poly and vinyl esters.
(
http://www.uscomposites.com/polyesters.html.)
Hope I'm not breaking any rules by posting a link.
Vinyl Ester