I've found a partial cure for it, when in really tough green alfalfa seed spinning the rotor up to 900-1000 seems to stop some of the banging noise. It also seems to cut down on some of the rotor loss in green tough conditions. The best is obviously to get the crop as dry as possible but once the seed has been defoliated 10-12 days its about as dry as its going to get.
If the conditions are good the 9660 sts is about 1.5-2 9610's its really amazing how much it will do in a day and it is a much cleaner sample. So far my best day with it was 70,000 lbs of A. seed. That was cutting from 12:00 to 7:30PM. Our 9610 was cutting in the same field with me and delivered 35,000 lbs in the same time period.