ORIGINAL: cutaway
I made some "perfect circle" bits of plywood with that dowel type fixture.
Roughed the circle on my band saw, drilled a 1/4" hole in a board and put the blank on the edge of it, eased it into a belt sander until I got the diameter I wanted, then clamped the fixture to the belt sander table, then just slowly rotated the blank around.
Perfect circles every time. The same scheme with a belt sander/fixture should work for cutting down props evenly on both sides.
It does, depending on the pivot. The dowel in the board needs to be a snug fit into the hole in the prop and a tight fit into the board.
But keep in mind that the tip that results will be a very large radius (whatever the radius of the prop is), round tip if the prop is rotated completely past the sanding surface. Not a big deal unless you're looking for square tips, or want something like Top Flites Power Tips. If you want only the LE of the tip to be round, then bring the blade into the sanding surface with the LE leading and stop it when it's perpendicular to the sandpaper.