You know.. probably everyone will disagree.. but I never worried about it. I got my horse working and then I have this curb bit with fixed shanks.. it is shaped like the horse's mouth with a straight bar at the bars of the mouth and the center part curves upward in the shape of the horse's tongue between the bars. The curb strap attaches to its own slots about the bit and the shank above the bit has another loop for the cheek piece.
The bit COULD be severe depending on the adjustment of the cub strap or chain and the harshness of the hands. I started the horse with the curb strap fairly loose.
Then I just rode the horse. By the time I was doing this I had taught the horse to move on an indirect rein and had gradually turned that into a nice neck rein.
As a couple of weeks went along I just shortened the curb straps to the tightness I felt optimal. At some point I barely touched the bit (a little bump once in awhile if I needed it).. but just the very lightest of contact.
And that was it.. we were working in that bit.
I have not had a horse in a long time but I have that bit. Never had a horse object to it and it fit a LOT of horses. Of course I had nice heavy oiled latigo reins and a very light hand.
I have never seen another bit like it and I don't even recall where I got it. This is similar but mine has a stainless mouth piece.