The whole point of a half check collar is to train your dog not to pull. He pulls, gets checked, does not like the feeling so eventually learns 'No' and 'Heel'. At this point he should be obedient in a normal collar or a harness. Any dog that swings off a normal collar or pulls like mad on a harness has not been trained to heel. It does not matter where or what the dogs background is, positive affirmation works ie don't pull, come to heel you may get a treat etc. Too many people we see give excuses for their dog's bad behaviour, when it's a lack of discipline on the part of the owners. You'd be surprised how many Vets and Vet Nurses get bitten by dogs trying to treat them, and the owners have an excuse for them every time.