Hi very basic to you boys but i have never worked with epoxy before ,so be gentle.

Thats hard to say. Not having played with ply much myself I wouldnt be able to compare the two fairly but to me it sounds like you are expecting one layer of glass to replicate the equivilent of 10mm of ply, and that sounds a big ask!!.

Perhaps a couple of tests with offcuts are in order? keep adding layers of glass or increasing ply thickness until desired result is achieved.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant