I'm seeing a lot of talk about propeller harmonics.  Just to show how difficult it can be to assess, a propeller for a turbine (no piston issues) can suffer large destructive harmonic problems even at idle.   Even a expert company like Hartzell got sideswiped by the unknown mode.  It eventually caused the loss of a hub and the aircraft in flight from progressive damage at idle.   I suggest nobody can assess the full interaction of a propeller and engine unless a full set of tests, outfitted with sensors, is accomplished.  Anything else is speculation in my opinion.

Paul
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