Hi, I´m Richard from Sweden and I own a RR Griffon Mk58
Very intereseting thoughts in this topic!
Griffon is one of few aero engines that are rubber mounted via a complex rubber system, or am I wrong?
This shows the had vibration problem in the first place, they also try to solve part of the problem with counterclockwise crank rotation.
I don`t really know, but I would not be surprised if they also run the engine in “odd fire” to prevent unhealthy crank vibrations.
By odd fire I mean they maybe have serarate the even firing order from 60deg crank to some +/- 1 to 3deg from this (57-63deg)
This is not easy to detect without a proper timing disc mounted on the crank and check against a ign. timing light.
Somebody with experience of regrinding Griffon crankshafts can maybe answer this question!?

Best Regards
Richard

http://www.griffon-engine.se