Basically you have a standard layup. This has plenty of strength for "normal" conditions. If you need more strength you can add more layers. You will get all sorts of controversy considering whether two 4 oz. layers are actually that much stronger than a single 6 oz. layer. What about 6 oz s-glass, or some other weave, or combination. There are many variables for strength. I just added two layers of 6 oz...for a total of three on the outside and two on the inside of my kayak...but I have a "need" for added strength and I'm trying to make the best of what I currently have. The future will see different types of layups for my specific use kayaks. However...your question concerns two different things. It really doesn't matter how many layers of glass you put on...you're still gonna get scratches and gouges...IF you paddle in areas where such can occur. Resistance to scratches and gouges CAN be a function of the material...ie: e-glass, s-glass, kevlar, dynel, etc....that you are using, BUT it might be said that the hardness of the epoxy and/or the additives to the epoxy are more important to scratch and gouge resistance. If you, or I, or anybody, can come up with a good formula for scratch resistance, then we'll be sitting on easy street. As it is we...or maybe just I...will have to continue experimenting with additives (such as cabosil, graphite, rock flour, etc.) to the fill coats on the hull for scratch and gouge resistance. The problem with additives is that it usually will dull, or completely cover, the beauty of the wood. Not too much of a problem in my case on the hull...but some people want the wood completely exposed to show the inherent beauty. I don't find scratches or gouges very difficult to repair after a season....but then, I'm not trying to maintain museum pieces. I will someday though. Decide what your requirements are, then build to fit those requirements.