Steve, I'd be curious to see who another layer of 4oz s-glass would compare to a thick layer of amended epoxy. Some of the things a person protects the wood from are abrasion, abrading impacts, and impact. A thick layer of goop does well for abrasion but I wonder about the other kind of wear. Why not simply add another layer of fabric then use fill coats that are amended with cabosil and white pigment? You'll have more goop to abrade but more importantly there's fabric there for sharp impacts.