I find this all really interesting. I campdraft, which I suppose is similar to the cow section of working cowhorse.
Campdrafting is done, on the whole, in snaffle bits. From the greenies right up to the open horses. I honestly can't even imagine doing a draft in a curb bit with a draped rein.
I wonder if the training of our draft horses is not as good as it could be because of the lack of progression in bitting. Or wether the use of a spade bit wouldn't be compatable with drafting.
I have always wanted to train a horse to a curb bit and/or a bosal, but I am always worried it will compromise their performance in a snaffle, which is what we have to use for competition.