In my experience my quarter pony was abused in the mouth by her previous owners. In her case, she rushed when ridden - out of fear. We had her teeth done, because the previous owners didn't keep up on it. In the beginning, i rode in a dr cook for awhile and worked on trust and gas pedal/breaks by using seat and verbal cues. She has a teeny mouth, a low palette and fat tongue, so I have found that she is happiest in a ported myler. She's slow and relaxed in her work now. It has taken forever to get her to this point. I know people have mixed opinions about mylers, but for my horse, it works. We have a combo bit of theirs too that we use for jumping and I like it because with the way it is set, it is riding mainly off of nose pressure. She loves it. If you are nervous doing bitless or a hackamore, maybe give that a try? and with my experience with a kineton, I have found that I do lose some steering. But in the case of the kineton, it really helped slow my previous horse down. I used to save it for the XC course when he got fast and ignored me. I wouldn't use it in a riding arena. It was saved for those times when I felt like things could get out of control. It's not harsh, but it is overkill if your horse gets a little rushy at the jumps. Make him comfortable, get him relaxed and work on using that with your jumping.