There is a horse in my barn that is a cribber. He cribs worse than any horse I've had this experience with (never owned cribber)... to the extent that when he came to my farm, he his top front teeth were barely visible beyond his gum line. Ouch, to say the least. If he doesn't have a collar on (only "preventive" we've found to work with him), he will get a mouthful of grain, crib, chew, crib, chew... inevitably loosing most of his food, or he stands at fence posts outside cribbing and ignores the grass/hay).
The owner has brought out several separate cribbing collars. The first was a Miracle Collar, which worked when it was fitted snuggly (two fingers under the straps) while the horse's head was in resting position. The second is the "Dare Collar", which has a 3x5 block positioned under the throatlatch. I fitted this "single strap" collar to "two finger" snug in resting position as well. This horse wears his collar inside and out, and it is only taken off when the owner is handling/riding.
The dilemma? The owner and I have discussed how tight this collar should be several times... I have routinely "tightened" the collar to a "two finger" gap while his head is at/around whither height. He has not EVER had wear/rub marks or sores from it. He still cribs occassionally (but not incessantly). Owner then comes out (couple times monthly, at most), puts the horse in crossties (with horses head UP because of cross-tie position), and THEN tries to undo the collar, which results in a tight fit/difficult removal. I explain to the owner to remove the collar before putting horse in crossties, as it is likely uncomfortable, and the owner insists that I've ratcheted the thing down too tightly, regardless of crossties or not. The horse has yet to demonstrate discomfort unless he tries to crib (discomfort exhibited by attempt - thinking for a second - doing something else) - or, unless the owner puts him in cross ties with the collar on.
I don't know what to do. It seems pointless to have cribbing collar and not actually use it to make the horse STOP cribbing. I KNOW they are uncomfortable when the horse tries to crib (or hold his head in a position resembling that which the collar is intended to prevent, which may or may not be a typical "play, excited, etc." position, depending on the horse). It is certainly debatable how humane they are (which is worse? Cribbing, which correlates strongly to colic and other health issues, or preventing the cribbing?)
This horse has already caused hundreds of dollars of damage to stalls (owner has willingly paid for damage repair above and beyond reasonable wear and tear). When the owner comes out, she returns him to his stall either sans collar or with a collar loose enough that the horse cribs on anything in reach.
One thing is for sure - I will NEVER purchase a horse that cribs, no matter the severity.
So - again, how tight are these collars supposed to be? It seems like it would be slightly variable depending on the severity of the horse's desire to crib... I have a feeling there will be lots of contradicting answers here, but... worth a try. I should also note: owner and I definitely don't argue about it. We discuss the why/how of what we each do, then kind of shrug our shoulders and move on because I guess neither of us has a "definite"... her vet told her if the horse doesn't pass out or get sores, it isn't too tight (so, I guess I've been going by that, lol).