It sounds like you could answer this question.

We had the prop on our 172N dynamically balanced a couple years ago and the
plane was smooth as silk. The prop was put back on rotated about 40 degrees
from the original position because that is where it was smoothest. This
resulted in it always stopping vertical which was a pain using the towbar.

That shop went out of business and we just had the engine rebuilt after
premature lifter failure. The new shop insisted on putting the prop back
according to the service manual instead of the index marks. It's hard to
tell with three months of no flying in between but my impression is that it
is not as smooth.

Another shop I talked to about rotating the prop back agreed that
positioning according to the shop manual is important (especially on a 4 jug
engine) because of internal torsional vibration and stress issues that do
not create noticeable airframe vibration.

We don't have anything I would call vibration. It's more of a buzz that you
hear rather than feel.

Do you think we should have the prop rebalanced?

--
Roger Long