The more and more I advance in my horsemanship experience, the more I think the Myler brothers have it right.......that when you have resistance from a horse you need to go with less tongue pressure (and less pressure in general) not more. I think too many "english" riders think they are being kind by riding in a snaffle and then they have to strap the horse's mouth shut to try to cover up the evasion. And riding with contact to boot. Western riders may ride with more bit, but at least it isn't "on" all the time.
I think if you have to strap your horse's mouth shut, either with a cavesson or the Equi Smart Control contraption, you should take it as a sign you are doing something wrong, not that the horse is doing something wrong.
Here is Myler's take on bit evasion:
To me, it was sort of an epiphany that ports are less severe than two and even 3 piece snaffles. And my horses can back that up.......I am now riding my two broke horses in a Myler #33 mouthpiece with HBT shanks and they do much, much, much better than they ever did in two or three piece jointed mouthpieces with or without leverage.