Aaron; I've been running at a 4 concave, 650 rotor,(high side) 900 fan for soys. They test 9%. No cracking. This machine is similar to your own in the description you give. As for corn, 5 concave, 1000 fan, 500-550 rotor (low side). I've tried lower rotor speeds like some of the guys in this forum, but then the capacity is hurting to where the ears can't get thru the cone as fast as the feeder is delivering it and the machine will shudder because of the crowding effect between the feeder and the impeller (or elephant ears) Then, a slower ground speed is in order, but to me, that's a waste of time, fuel, and machine, as I ordinarily would drive 5 mph or as fast as the head will take 4 wide rows of 18% corn.