I ride my older QH mare in the arena with just a plain snaffle. However, when some of my barn buddies and I trail ride, we like to race through the fields. I definately have the fastest horse, but she doesn't like to stop. I changed her "trail bit: to a twisted snaffle, but it didn't help that much. I also have a tie-down on her as she throws her head. I have tried someone else's Dr. Bristol and it did nothing. Any recommendation?