After reading all the pros and cons above. Whats the chance of getting a set of Skeeter main rotor blades, head and transmission? No it won't have high inertia, but will be considerably lighter than the weights you are discussing. To carry this statement to an extreme; make your own plywood and doped fabric blades, and utilize simple belt drive reduction. The head flap system would not be hard to make as its got a short usage life. Last thought is wear a good crash helmet.