RE: Great Planes Prop Ballancer
Not sure which balancer you have, but it's possible you might not have the tapered pieces that hold the prop getting a good center. Make sure you are getting a good hold on the prop with them, and the hole in the prop is not buggered up to the point it gives an inconsistant hold. I use the Top-Flite magnetic balancer for smaller props, but bigger props are too heavy for the magnets to hold, so I use a fingertip balancer for big ones. If you're using a fingertip balancer, use a gentle touch to hold it to allow it to spin easily.