Look at all those clinics where trainers take wild mustangs and within 3 days they have them halter broke and are riding them around. With out the horse ever getting upset or bucking. Anyways thats my soap box and my experience with whether a driving horse can be successfully and safely pulling a cart in less than 6 months.
A driving horse is a whole different ball game. You have attached a "weapon" to them that can hurt them. I have know plenty of horses who have had wrecks with vehicles and now will never drive. I can't say the same thing about riding horses.
I would say that your techniques are quite different than the professional expert driving trainers that I know (local, national, and international). If it works for you, fine. I have made the mistake of confusing "acceptance" with "readiness" and had disasterous results. Yes, I have had horses that went from harness to hitch in six easy lessons, but those were the rare exceptions. When I am training, I will take the time to actually "push" my horses a little so that I know what their "breaking point" is. I want to know what is going to make them "freak" or spook before I even put to and help them understand how to work through it safely (John Lyons calls it "spook in place"). It's not a matter of "if" but "when" they spook, even with our absolutely quiet horses. Those are the ones that I am MOST leary of because when they blow, they blow fast and hard.
Just this weekend we were at a Horse Fair and a kids driving group was on their way into the arena. One of the minis blew up and reared (with a header) and fell over backwards. My husband and I happened to be standing right there, so in true carriage driver fashion we jumped right in to help. We told the adults to get the mini's head down, but unfortunately his head was on top of the shaft facing the cart, so an adult held the horse's head. This didn't really keep it from thrashing as we were trying to get it out of the tangled mess. I told them to release the backstrap as that would drop the whole back assembly of the harness (my hands were full of stuff for the next group waiting to go in the arena). The crupper had slipped off the tail and the breeching was under the horse, so we had to go after other buckles. My husband started undoing the saddle and found that the harness didn't have open tugs, but those modified wrap tugs, so even releasing the backstrap wouldn't have worked as the horse was "wedged" in the cart. They managed to get the harness off the horse without cutting something, but my husband was ready to get his jackknife out.
After that, the other horses started fussing and the kids kept jumping out of their carts, so I was running around telling them that they needed to be in the cart if their horse was put to. Each one had a header who was holding the rein instead of the caveson. If the first one had the caveson, they might have been able to pull the mini out of the air or keep it down in the first place. When I head, I have two fingers in the caveson and my thumb around the rein. That way, I am not mixing the signals either from what the driver is telling the horse. I also looked at their other harnesses, and instead of a buckle on the backstrap, there was a Conway buckle. Even if we were able to get to that downed horse's backstrap, we wouldn't have been able to get it off easily. These horses are supposedly so trained, that they are part of a kids performance group. It can happen at any time.
IMO (and a lot of other people) driving is THE most dangerous thing you can do with a horse (even with a mini) besides maybe bronc riding or steer wrestling. That is why drivers are extremely concerned about safety and accepted driving practices. I don't know of a equine sport that is
more about safety than driving. I have a friend who was giving a clinic to a 4-H group and going over the proper methods of handling a driving horse. The 4-H leader told him that they weren't concerned about safety, they just wanted to have fun.
Needless to say, he didn't put in a lot of time there anymore if even the leadership for the group wasn't going to listen. You can't have fun if you are not safe.
You can't teach a kid what numbers are and have them dividing them in the same day. I write this so that anyone reading understands that this is the exception rather than the rule with driving horses.
Myrna