I think this is another case of the old saying, "There ain't no free lunch." Chopping fresh, probably juicy, corn stalks takes lots of power. That is why they put 500 hp engines on forage harvesters. And most combines, especially rotaries don't have any power to spare. They are also not designed to deliver the power to the header needed to chop stalks. So I guess its go slow if you want to do two jobs at once.