Most organic buyers allow .5 to 2% so, separation of crops come down to distance and time.
If the crops pollinate at different times, no problem.
I understand perhaps 16 end rows is enough space to keep cross pollination from being a problem.
But every situation is different.
Pollen drift is a natural thing, so nothing you can do to stop your neighbor. If you could, then your neighbor could also sue you for messing up his crop, and there would be a real mess of lawyers..... Corn is a crop, if you want a special, different crop it's up to you to protect your special crop.