Hi Anthony:
Sounds like to you have the right message (i.e. I am the leader), but perhaps need a louder voice. I have never had a need for a chain shank (see attached image), but I think it is warranted in this situation. I think this tool would increase your “voice” until your horse gets the message that he can’t run away.
I suggest someone lead your other horse while you lead Sunny. Ideally you can anticipate when he is going to take off and remind him to stick with you with a few sharp tugs. Make sure your chain shank is set up so that there is a release of pressure when you are not applying it. In addition to the chain shank, you can also start off with a driving whip or long twitch that you can wave in front of him as well if he is pushing ahead (bonking him in the nose might also be warranted). If anticipation fails, get ready to hold on with two hands to stop him.
Ideally you can break this cycle with these tools to the point where you don’t need to rely on them. If you can prevent him running away with a second person and these aids, try with just you making sure Sunny is next to you when you lead two horses. Eventually you should be able to lose the chain shank and twitch. I would, however, have him in a rope halter at all times if you don’t already.
Like Jay, I have a horse just like Sunny – uber-dominant, smart, hard-working, and always testing his boundaries. He keeps me sharp. Good luck with him and keep us posted.
George
