I am about lay fibreglass the kayak I am building. I unpacked the fibreglass cloth which I received via courier yesterday and as I unrolled it I thought that it looked quite thick. I am concerned that they may have given me 9 oz. cloth instead of 6 oz. My question is how do I know if I have the right stuff? If it is 9 oz. cloth would it be a bad choice to use it anyway?