A bit late but if you don’t have luck I’ll throw in my 2 cents anyway.
My old jumper would only ever curl up in a two- or three-ring, nothing else. I also didn’t like how I felt I had less finesse with the ring bits - I felt too disconnected from her mouth. She was very opinionated, and she had a few different bits she went in depending on the season/her fitness/where we were going. On days she was really fired - classes in a big grass ring, or hunting - I would either use a Mikmar combination bit or (solid) Nathe mouth hackamore bit. For being as strong as she was, she was very sensitive to rough or jointed mouthpieces but I found the combination of fairly gentle mouthpiece with the right kind of leverage and nose pressure was the ticket and I barely had to touch the reins. Those also allowed me to keep her mouth soft, so we could school in a mullen happy mouth loose ring.