I usually run it between half and three quarters, but maybe thats too much. The contents are usually half grain and half foreign material because I like to run my chaffer a little more open. Also I usually run the tighter than recommended sieve to make the grain more clean. I let the tailings determine how tight my sieve should be. Too high of tailings, open the sieve a little more. 180 bu corn the sieve is on 5 for the light weight and small corn we have this year. Have the deep tooth chaff and sieve.