Actually, probably less likely for a single than a twin. Lower excitation frequency. The shaft will have snapped due to TV. A crank between two flywheels is a stiff system. Making it stiffer OR reducing the excitation frequency will both reduce the likelihood of failure. If you want a direct drive prop on the PTO end, you really should consider removing the flywheel completely. They are around 20lb for the v-twins, so there's a lot of of incentive to do that. Yes, you'll need a new ignition trigger. But it's just a magnet.