Tony,
I’ve see some people using a Gas airplane prop. Can’t find that article anymore. They had multiple props same pitch, but cut the prop diameter to allow more RPM’s.
Ron
In airplanes most folks don't bother with bench running and just do it in the air avoiding long durations of full throttle until engine has a little time built up. What are the benefits you expect from bench running?
I have run Zenoah's in maybe 15 boats, there is no real break in needed, I would say don't use a synthetic oil for a few tanks to help let the rings break in. Other then that go run it, Colman camp fuel with 8 ounces of oil per gallon.