I've been working coming a five year old for the past few months (he turned five about a week ago). We've had some "ups and downs" but on the whole he's got an excellent temperament (if a bit skittish) and an easy-going disposition.
He's had trouble accepting a bit. We know he has a dentition issue. He's got a pair of canine teeth that the vet. Said could make him a carnivore. Pulling was not an option for multiple reasons; she's been floating them for the past year to get them down to the point where they will not interfere with a bit. He was done last Tuesday and on Thursday our instructor was due for lesson. He's been off for a week as we were out of town and I wanted to get him back to work. So I resurrected a side-pull that had been in our tack closet for several years.
We fitted him and then I tried him out. It worked!!! He was way less "mouthy" and moved much more easily. He has a tendency to "nose out" and I was concerned that there might not be enough "authority" to keep him in check. There was. With this device you cannot get into a "pulling contest" with the horse. If he starts to root or nose out you MUST release the straight pressure and use lateral pressure to turn him and get his attention back. You MUST sit squarely and have effective use of leg and seat. We worked for half an hour and, at the end of that time, he was moving pretty much forward, straight, and calm. When he decided to "test his limits" I found I was able to "shape" him a bit and demonstrate that I was still setting the limits, not him!
We went out today in high wind conditions and he was "wary" from the time I brought him to the barn. The first couple of minutes were a bit dicey, but he settled nicely and we had a productive, if shortened, session. He gets Mondays off but we'll go out again on Tuesday for an extended work period. I want to see he does when he gets a bit fatigued.
One of the THE hardest things in the world for a rider to do is to reduce contact when a horse starts to get "strong" or "resistant." The temptation to "tighten up" is really powerful. But it's almost always the wrong thing to do. All you do is make the "spring" more compressed meaning that when it lets go it will go with real force. Reducing contact and adding some lateral "shaping" will prevent that "compression" and if there's no tension in the spring then there's no negative consequence when it releases.
The side-pull can also be useful in developing softer hands and more effective seat and leg aids because no matter how hard you pull you won't make much of an impression on the horse; all you'll do is make your hands and arms tired! But slight leg pressure and some "finger sponging" will get you what you want with much less effort. What's not to like!!!