I'm hardly a propeller expert, but I'm sure some pics would be helpful for everyone to see what you have. I would say that most vibration issues stem from simply having poor, uneven flow to the prop, but certainly the mfg rep's suggestion could have merit too. Have you done any calculations to see the relationship between engine firing and blade position? Could the prop be easily rotated relative to the engine (at the coupling)? Has anyone measured the vibration yet?