A friend of mine that grows bamboo recently sent me a couple of bamboo sheets. These were just cut from regular bamboo and so there was the outer skin still on it and was very convex. I tried different ways to sand it down to make the convex area flat so I could draw an outline of the scale, but I am finding it very hard to get it flat. Does anyone have experience making bamboo scales? What need to be done to grind it down to the proper thickness and flatten the convex outer side?