Three degrees positive incidence on the rotor blades relative to each other is mentioned - that would result in the rotors spinning the wrong way! Negative incidence is required - note that lift is still generated due to airfoil section. I find simple rotor hub made from 1/8th ply and polypropylene hinge is fine - cheap and simple to make. I now always have a 15 degree `delta` angle so that blades are made set at zero incidence which adusts itself in flight.