My SSH is exactly as Gilhermie describes. Normally, if I loosen the reins she speeds up, looking for the bit, and will get faster and faster.
I'm by no means an expert, but think this is why the curve is most often used with walking horses. The amount of contact the horse is looking for, or the amount of pressure on the reins is easier in a curb.
I personally use a medium port, but the people I bought her from used a twisted wire.
Gilhermie, thanks for your insight. You just explained what I knew to be correct, but didn't understand why. I think now, I can make the next leap with the information you just provided me. It's starting to make sense. Can you elaborate on bascule?
For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places.