I have one! I have used it w/great success on my muley-girls, but typically ride the ponies in sidepulls or halters [see Wynk's pix]. As soon as they know the basics in a bit (whoa, go, turn R & L), I drop it despite the protests from my more purist riding-buddies.
[Several yrs ago, one of my friends was urging me to at least put a ring snaffle in Quig's mouth as she watched me muscle him down from the 20-MPH canter he WANTED to take DOWNHILL as camp was in sight, to a more manageable 14-MPH extended trot... I told her, "Honey, you think he acts bad now - believe me, he's much worse when I put iron in his mouth!"]
Try it I think you & Missy both will like it!

Thanks Val. Like I said, I've been riding her in a hackamore and people are always stunned that I do as well as I do. The bit just does not work, her teeth are configured a little off center and anything in her mouth causes issues. Do you have the Dr. Cooks model?

I've never used one, so no help from me on that. My horse Dusty used to chomp on the bit and constantly toss her head up when I got her. I remember buying her an apple mouth bit and she actually took a piece out of it by chomping so hard. Anyway, I'm sure you've already checked Miss but Dusty had a tooth that needed pulling and the rest were floated. She was much better after that. If you get the Dr. Cook's I hope it helps.

Thanks for the comment. Missy's teeth are configured strangely and even with a hackamore you can tell when something in her mouth needs attention because she starts to toss her head around and be naughty. I'm hoping that with a truly bitless bridle instead of just the hackamore it will help me to control her a bit more without hurting her. I will keep you posted.

Yes, mine is a genuine Dr Cook's...
It's about time for me to drop the bit out of Miss Scarlett's mouth; she was head-tossing & fidgeting yesterday. I'll probably try her in the bitless rig since it is sized for that "larger" [TWH] head of hers!
Also I had to swap Quig's new sidepull w/Baraq's heavy-braided noseband-halter, since the noseband was rubbing Mr B's sensitive lil' hide [it was too big for him anyway as you can tell since I could let it out enough to fit Hefty Quig]. Baraq still tosses his head when he gets bored, but I think that's just an Arab thang...

Have you ever had her teeth floated? It is something that needs to be done regularly... once every year or two. even without a bit it could solve some mouth problems. I always rode my Big gelding in a bit but just an easy snaffle... I have been leaning more and more towards natural horsemanship however. Have you ever looked into Parelli or the other schools of though on that matter? I have posted quite a few vids on my facebook from them lately. Definitely worth looking into.

Your horse sounds scary love... If they have to drug it so you can ride it is just hiding the real issue... that she is unsafe. I am scared for you!