Forget corn....that's easy. Try to get it to distribute all the material evenly in small grains with high chaff loads. It works great some days, then terrible the next. Bleedred has it right...way to picky on how it works. And it most certainly thrashes unevenly. When we changed out our wheat concaves for corn on a 2.5 year old machine some of the rasp bars were COMPLETELY wore off....like gone! Totally uneven wear, and yes, it was all leveled out properly.