Brandon, If your goal is increased abrasion resistance then I'd first identify the major areas of abrasion: bow,stern,area under seat,area behind coaming (paddle entries), coaming, foredeck where paddle whacks it. Then put extra material as needed whether that is a thicker coat of epoxy, thickened epoxy or extra glass/fabrics as needed. I'd suggest a couple layers of dynel strips at bow and stern or at least 3 layers of bias cut 6oz on the bow/stern wear areas (only a 1" by 6" strip where the ends of the kayak touch when lifted at one end. If you are considering a major wear resistance then go ahead and put down another layer of 4oz glass on the bottom panels, that should add about 12oz to the kayak. Personally I don't think flat black graphite is a great idea if your kayaks are sitting upside down in hot sun. There's no reason to turn a perfectly nice kayak into an oven. I like non-skid marine tape (2"x4") behind the coaming for paddle float and other paddle pressures, it also helps keep the paddle from slipping around. 6oz on the coaming isn't a bad idea even though the 6mm plywood is plenty strong I find that some of my boats have stained wood from water seeping in after an entire summer of T-rescues and being crammed against other boats on racks. A kayak that tumbles to the beach without you will hit the coaming, so 6oz there will add further toughness. Deck whacking gets taken care of by a glassed deck but also simply running a roller of epoxy over the sheer at the deck whacking area works. Hey, I even haven't got started in over building recommendations! But back to one of your questions , 6oz glass and epoxy is tough enough,but for a 230lb guy and 100 lbs of stuff there's nothing overbuilt about 10-12 oz on the bottom. Check out Nicks book on recommended glass layups for his strip boats.