Several months ago, there was a thread on balancing the flywheel after turning the fins down to the hub face. Someone asked about the balance of the original flywheel before modification. I finally remembered to dig out the spare and check its balance as I said I would.
Verdict: The orginal is as out-of-balance as the modified unit was ! Interesting fact is the heavy side of the original is the magnet, which precludes drilling to balance as I did the modified unit.