my horse cribbed with the miracle collar with the wool covers and still rubbed hair off. nothing stopped him from cribbing. just like your boy jager will crib on anything and everything including the rope he's tied with, brush in his pasture (the fence is electric), buckets, tubs - ANYTHING. the best i've found to do is to manage everything else about their life (diet, exercise, etc.) to make them as happy as possible and that will lessen the cribbing but, at least in my case, there is no way he's ever going to stop. it's more a matter of managing the "damage" than anything else.
just my two cents.