Are you asking for corn grain or snaplage?  

We use our feed truck at times, but we get in a weigh wagon as well.  Plenty of times, we dump weigh wagon into a semi or our big wagons, and the entire plot  then goes over a certified scale.  Always been extremely close

For yield checks, we do the 17 ft 5" and hand shell ears, then have the elevator give us a moisture %.  It's 100% accurate for that small area