You can continue to use epoxy, I only recommend a polyester laminating resin for bonding the transom together. I prefer polyester because that's what the boat was originally built with. But you have to follow the rule - epoxy will bond to cured polyester, BUT, polyester will not bond to cured epoxy. So, in any case where polyester is to be used the surfaces must be ground to fresh fibrous glass for bonding to occur. Evercoat has a laminating resin that comes in a quart can, should be plenty for the transom.