Well, there's certainly nothing wrong with the balance of the single rotor parts, because it's smooooooth as can be now that the redrive and prop are gone.  Below 1800 or so, there's some shake from the lack of flywheel weight, but it runs down to 1000 rpm or so without being too bad.  Above 2000, up to 6000 rpm, it's true rotary smooth.  I guess I just need a redrive with a suitable dampener now, but that's not going to be any sort of priority until the RV-8 is done.  Unfortunately, that kit was delayed, and I won't even get it until the first of March.