Ramen,
I beg to differ with you about different operators having different methods that directly affect the operation and stress on aircraft in the same role offshore.
Take yourself back to the Helicopter Services experience in the S-61 Spindle Shucking contest on the North Sea....they won 2-0 over Bristow as I recall.
All laid down to an RPM issue during particular maneuvers.....I am sure some old North Sea hands can add the details for you.