Harness & wagon fitting queries

[DownUnder Gal]

Need some advice please. Our current challenge is how to stop Koby from tossing his head up and down when he wants to go in a direction away from where I want him to go. We've introduced the whip and it is working quite well, although I need to practise co-ordinating my own hand movements better.  Koby is SO strong, he almost pulls the reins out of my hands when he puts his head down and tries to go towards the paddock gate where his buddies are.  My current answer to this is to make him halt, then "back" (the latter which he is now very good at) and also we go around another circle of the paddock to show him that kind of behaviour only means more work for him.  I always ensure we end the lesson on a positive note.  Maybe it's time to take him away from our property so that the distraction of his friends is removed altogether.  At the moment I feel it is a battle of our respective wills and the fun factor is waning.  He definitely no longer seems concerned about the cart behind him and you can see his brain ticking over, wondering how he can outsmart me.  I am still ground driving from out back because I don't think I'd have complete control if he really decided to assert himself in one direction.   Any tips?