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Could a single bladed rotor that is unpowered ( not powered by rubberband or anything else) qualify for the bonus?

No, as per rule 3.e, rotors must be the lifting surfaces. If a component is not powered, it is not providing lift. Para 3.f, last sentence: A blade is defined as a single surface designed to create lift force as it moves through the air. An unpowered blade is likely to be stationary, so it cannot provide lift.