Is 3 oz of Callisto a  'good rate' on heavy land? 

I know the dual rate in Halex GT is light, unless the Callisto is really heating up the dual.  I don't mind spending the bucks if the stuff will work.  Otherwise the RU/ATZ is a know system, which is not perfect, but will keep it clean enough to harvest but not 'clean' for most farmer's eyes.

Also keep in mind we will be harvesting this corn in late July.  If its wet when the corn drops its leaves whatever little weeds/grass is there will explode in a matter of days.  We don't have the 'luxury' of cool temps/short days keeping the summer grass/weed pressure under control as those in the northern climates do.