Sam, I'm with you regarding gouge/abrasion resistance,,that's mostly a function of the thickness of the layer and the nature of the cloth,,I don't think 8oz of multiple fine weaves will be much different in gouge resistance than one layer of coarse weave if the total thickness of glass/epoxy was the same. So two layers of 4oz will be more durable than a layer of 6oz,,it's more glass and epoxy. The difference in impact/tensile strengths I think exists but again will be more affected by whether one is using s-glass or the different cloth is a significant difference in weight. I've noticed 6oz glass fracturing with waterstains in ways that two one or two layers of 4oz s-glass does not. But there again one layer of 4oz s-glass isn't as hard as one layer of 6oz e-glass and two layers of 4oz is more than one layer of 6oz.