To: Shawn Coyle. .. .Did you Russian friend say anything about vibration? Many US helicopter blades are mass balanced to ¼”ounce to minimize vibration and oscillatory loads in the rotor system. I have heard of that being done on propellers in fact I saw it being done. In the 1947 Air Races a pilot named Howard Lilly who I believe was a NASA pilot cut several inches off of his prop on a Bell King Cobra. He ran the engine and there was a bit of vibration so he removed it and balanced it using a file to cut away the prop material until the blades were in balance. The race was won by Cook Cleland flying a Goodyear F2-G Corsair with an R-4360 up front.