Well, soloudinhere, one particularly boring summer I decided to ride bareback (a very hot muggy summer) and ride in just a Weymouth curb. My horse went very well in a snaffle, and he went well in a double bridle, I just thought it would be something to relieve both of our boredom during that long hot summer, something that neither of us had done before.
I ride Forward Seat, so I concentrated on allowing him to go in his normal head carriage in the snaffle, head down, nose poked out, open throatlatch, with a light rein. After a few weeks, since he had shown me NO OBJECTIONS to my use of just the Weymouth curb I cautiously started keeping contact with the Weymouth curb at a walk, concentrating at all times with not changing his head set when I rode on contact (just like with the snaffle.) The rest of the summer we went a lot on contact with the Weymouth curb, at a walk he fearlessly reached out for contact and kept contact just fine. After a week of so of being successful at a walk I tried contact at a trot but my horse put his head up and went into a more dressage type of head (neck smoothly arching upward, nose more in, etc.,) but since I was trying to keep him in the Forward Seat physical stance I admitted defeat and just rode him at a trot on a sagging rein, same cantering and galloping. After that summer I went back to mostly riding with a snaffle with occasional forays into the double bridle.
After a drunk driver drove his car head on into mine I was having problems with my Paso Fino mare, she wanted to eat grass, she knew I was weak as a new born kitten, and it was super hard and painful for me to get her head up. I spent an hour at the local tack store, trying each curb bit there (over 50 of them) on my arm to choose the one that was strong enough for me to get her head up while not torturing her mouth. That curb I selected ended up being her favorite bit of all time and we had many, many happy hours of trail riding using this bit. I could not keep contact with this mare with the 7" shanked curb she liked so much (she went behind the vertical) so I rode with a sagging rein. So long as she strode forth confidently, did not go behind vertical, and obeyed my directional and stopping aids promptly I really did not care, I just wanted to ride her without further injuring my badly messed up back.
Both these horses taught me never to do a dead pull on the curb bit. they taught me to release my hand aid immediately, and they taught me that the curb bit demands a greater release of a rein aid than a humane snaffle. My first horse was ALREADY light in hand, while willing to accept the much stronger contact for galloping/extended gaits, and he never went behind the vertical although his neck/head conformation made it super easy for him if he had ever wanted to. The Paso Fino mare was also light in contact and light in obeying my hand aids, I just needed help getting her head up occasionally when she saw a particularly lush and yummy clump of grass.
My current riding teacher will let me ride with a double bridle on some of her lesson horses because my riding teacher absolutely trusts my hands after giving me lessons for around 12 years now in spite of my problems with my Multiple sclerosis. I am the only rider at her stable who has this privilege with the double bridle (I provide the double bridle). When I want to try out a new snaffle, Kimberwick or Pelham bit she lets me do it, and sometimes she tells me I am the only rider at her stable that she would trust using the particular bit that I want to try out. After a ride in a new bit we discuss the ride and how the horse reacts to the bit. If the horse obviously does not like it I go back to the acceptable previous bit that the horse has done well in.
My riding teacher has put me on several horses who had real problems with accepting the bit because I have proven myself to her, and her horses. She enjoys seeing me turn compulsively inverted, gaping, and hostile horses (who ran away from the bit with her other students) who suck back at any hint of contact into horses who reach out for the bit calmly when I ask for contact, and who will willingly KEEP contact with my hands with relaxed mouths and lower jaws. True lightness comes mostly from the correct timing of my hand and leg aids, then it is super, super easy once the horse understands what I am saying with my aids.
Just because some riders do not ride exactly like you do does not mean that these riders cannot ride at all.
Some horses simply prefer a curb bit (Weymouth, non-jointed Pelham, non-jointed Kimberwick) to any snaffle bit out there. I take the viewpoint that it is that horse’s mouth, I train for acceptance of the snaffle first, and if there are still some problems I often find that the curb type bits are the answer for these horses to get them to go forth boldly and confidently into the world. Some horses just do not like bits that jangle in their mouths like jointed snaffles do, and many of these horses ALSO do not like Mullen mouth snaffles though they will obey them before they learn how easy it is just to lean on the Mullen mouth snaffle so I have to carry the weight of their head. These horses are often much happier in non-jointed Kimberwicks, Pelhams, and in double bridles, and since the horses are happier I am happy.
The horses I ride will obey, while on contact, me moving my finger maybe an 1/8 of an inch with maybe a gram or two of weight on the rein, in snaffle bits, in Kimberwicks, in Pelhams, and in double bridles, for hand aids. Is that light enough? Of course going faster the horse does take a franker hold on the bit so I may move my finger up to a 1/4" with two to four grams of weight on the reins. Is that too heavy? (Note I said grams, not ounces or pounds of weight for my contact.)
As far as expensive bits are concerned I have had great success with some of the titanium mouthed bits. I have particularly enjoyed riding with some of the Fager bits. Otherwise I usually find that the regular bits work quite well with my hands as long as I listen to the horse.