Didn't think of that one.  Good point. That'll drive the single rotor's effective cost up by a grand or two.  Richard Sohn, you used one of Tracey's redrives, didn't you?

I’ll tray again.

    I am using a G40 gear box from Hirth, including the donut rubber coupler. The ratio is 3.33:1 . Never had any problem in 50+hrs ground testing.