Short and quick, our dry fertilizer spreader came unhooked again today (Dalton 800 single axle) (it was back heavy as always) and one of the chains held and broke, and the other chain was loose and didn't do a darn thing.  Both of the spreader spinner wheels were ruined and wiring harness was mangled.  

So what is the best way to keep corn stalks from unhooking the safety chains on implements?

I don't use the snap type of hooks on these chains but use the sliding type of hook to keep the chains on.  Then I try and wire the sliders so they won't come loose.