When I rebuilt a Stuart Turner S9, I used a gib head key as the sole means of attaching the flywheel to the crankshaft.
On my hot air/Stirling Engines I fit the flywheels, and pulleys with two set screws at 90*, and these are usually brass screws so that they don't damage the shaft, they are done this way as the pulleys are changed often, and the flywheel is taken off when the motor is transported. They are not scale motors, but motors in there selves, ranging from 3/8" bore, to 2 1/4" bore, and flywheels from 2" dia, to 6" dia, the heaviest around 900gm. A bit OT I suppose, but that's me and flywheels. Ian S C