Over the past four years, I bet we've planted 500+ of them.  Nichols always said they had never known anyone else with problems. 

Tried a hundred different ways of install, short of welding them on even.  This year, we went back to bolt on ones.  At least the neighbors won't have to bring back the ones they found on the road. 

Seriously, I found that if you install them, and go right to work with them, the chances of losing them are somewhat less. 

So far this year, we have found 20 of the lost ones in our spring crop fields.  Luckily none in a tractor tire yet.

We always used the 18" high crown sweeps.  New springs with each new sweep.