Every horse I've had was Hackamore "trained". Actually, I just rode them with a halter most of the time! Since having so many halter/bit/hackamore horses, I have taken the time to do some research.
If your horse needs a tougher bit, it needs a tougher Hack, therefore, probably without padding underneath.
I am pretty much going to say all I know.
The Hackamore is meant as a...no-air stop...so to speak. The bosal or noseband is placed above the nostrils, but still on the soft track of them. Does that make sense? So when stopping or slowing with a hackamore, a pull-and-release motion is required.
This is the hackamore type I have...see the padding? That is important.
This is a mechanical hackamore for those medium horses.
And here's the heavy hackamore for those tougher horses. And I think this is an older pic.
There are also rope-noseband hackamores. Do you have any other questions??? Hope this helps! Guys....I am sooooo sorry for such long posts!!!!!!!!!!