I have a 67, am running concave between .5 and .8" and rotor at 450 - 525 air on 5. Chaffer 13 - 15 and sieve 7 - 8. I also have the cage sweep kit in which I really like from sunnybrook. Sunny brook explained it like this, when they put a cylinder on a test stand to balance and run it there is very little air movement off of the cylinder. When they put the sweeps on it creates a fan effect like a squirrel cage fan and in effect helps move the beans out of the cage. I also have the sped up chopper. Its all working excellent.