He will crib until the end of his days. You can attempt to thwart it, impede it, or reduce it, but all will fail. Put him in a pen that he can't destroy (no wood!) and just let him do it. Unless he shows signs of colic, I wouldn't bother with a cribbing collar.

A confirmed cribber will crib even when out on acres and acres of grass. It's a behavior they learn to do (generally while confined on a high grain diet) and if they get to do it long enough, it becomes crystallized and there's not much you can do about it. It's a soothing behavior, and those are the hardest to break b/c the animal LIKES doing it and gets upset when he cannot do it. It's like nail-biting, hair twirling, jewelry twisting (I can't leave my rings alone) or any other little bad habit a person develops.

Horses can and do gain weight even though they crib. Turning him out in a big paddock or pasture with lots of good hay can help decrease the frequency. If his mouth is busy munching hay it's hard to crib. If he's running around and playing with his buddies it's hard to crib. But you won't ever totally eliminate it.

I've seen horses crib on trees, rocks, even themselves. Some horses quit entirely when they're outside, but as soon as they go into a stall they start again. I've also seen horses who know how to get around the cribbing collar. A mare I rode would literally scratch her collar off, as well as most of her mane. Another gelding learned that if he put his head down and twisted the collar against his leg, he could crib.

Face it, he'll always crib, but there are things you can do to help reduce the damage he does to property and to himself.