stallions can be extremely difficult to handle. some are so territorial that they will try to kill anyone who comes into their corral or stall. and they cant usually be kept in the same enclosure as the other horses wether the mares are in heat or not. a stallions instinct is to drive away other males, once his sons reach around 2 years old he drives them away, unless he is too weak, then one drives him away. even geldings are perceived as a challenge. stallions are also very testy and if you turn your back for a second many of them will bite, and take out a chunk, or kick. if a mare IS in heat almost any stallion will go insane untill her heat is over. rearing, bucking, neighing and whinnying constantly and trying to tear the fence or stall to shreds.
I agree, why not geld him???
think 6 feet is too tall??? if he rears up how tall will his head be?? if his head is more than 6 feet tall when he rears then the stallion pen is too short. a mustang stallion, even one that is 13 hands, will either have no trouble jumping that if he really wants out, or he will get stuck midway and tear himself up. I've met a lot of stallions, only a few could be kept in a pen that they could see out of.