The vanes are in the factory setting we tried slowing them down and that dident seem to help. This year we did put 12 spike bars on the back of the rotor and it seemed to help some. Tried running the rotor from 280 clear up to 650 and the concaves from 2 to 7 seems to work the best rotor around 300 and concaves on 3. Ground speed dont really seem to mater we run around 4mph but have slowed clear down to 1mph and it still comes out the back.