I noticed today as I was preparing to take off that my P3A was vibrating on the ground before take off. It was sitting there as the props were spinning waiting for me to push the throttle. The whole craft was shaking. I know the props are balanced as I did it a few weeks ago. I replaced them with the regular white plastic type. Could the cf props be out of balance with nothing happening to them other than flying? I am going to rebalance them tomorrow to double check. Any thoughts?