It would depend entirely on how the motor is wound. I'm not entirely sure what KV rating to aim for, I'm thinking around 500Kv at the moment running on a 3S so giving a theoretical maximum of 5550 RPM without load. In terms of regulations I should be okay as long as the spinner can fully stop in 60 seconds. The spinning element will run above 500RPM, but will be less than 500mm in diameter and the spinning element will be less than 20% of the total weight. In a featherweight this would mean less than 2.72kg if I've done this correctly. The motor uses electromagnet coils on the stator while the rotor using permanent magnets.