Need help with a bit issue
So I am having an issue with a horse that I am training on barrels. This horse is trained to the T. He can back up, sidepass, spin, do roll backs, and all that fun stuff pretty much all with legs and very very little rein pressure. The thing is when I get him going around the barrels he really likes to go and he really gets into it. He has always seemed to have a very soft mouth and does not like you on the reins whatsoever. So when he starts going around the barrels naturally I want to keep some pressure on the reins to keep him slow and steady. Well I had put a little "s" hack on him because I could tell he didnt like pressure in his mouth and I thought this would work a bit better. He hated the hack, I mean everytime I would apply pressure to the hack he would put his head down between his legs and shake it hard from side to side. He also did not want to stop very well or flex with the hack. So last night I decided to put on the Jr. Cowhorse bit I had bought for a diffrent horse. It is the three piece dog bone mouthpiece with the copper roller. I immediately saw a difference in him. When I applied pressure he did not shake his head or put his head down. BUT he did not seem to respond to this bit at all! He wasnt fighting the bit he just seemed to ignore it. It would take several tries for me to communicate my que that I was asking through the bit. It was almost as though this bit was not enough for him. This confuses me since he seems to have a very soft mouth. I am at a loss as to what else I can try. I have gone through about 4 or 5 different bits on this horse and don't know what to try next. Please help!