Join Date: Sep 2011
Location: Germany- but not German =D
OKay firstly, a market harbre is a piece of equipment I DETEST. I don't have many, but that truly is one!
Your TB is pulling, because you can't give or take the contact, her head is fixed in that positiong so she's using her head and neck against you. If she's been raced, she'll need retraining to accept the bit. You don't need a stronger and stronger bit, espeically is you say she has a sensitve mouth, try a snaffle, get her to understand what a contact is. This will take a week or a month, it depends on the horse, and a trainer will be best to help you with this.
Please get her out of that contraption though. My dad used one, and he last two weeks with it, you have no way to give the horse its head. Using it for jumping is a dangerous, dangerous idea, the horse has no way to balance itself on landing if its head is tied up.
12 months in the UK working on a race track is 12 months working on a race track.. I'm really sorry to say IMO that doesn't make anyone knowledgable about TB's. Your's has been programmed to run, she needs reprogramming to riding horse. You need to sort out basics first, as bubba13 mentioned, ground up. You can't sit on her and expect woah to be woah, she doesn't understand it. She needs education, and you need to give it to her.
Finding a trainer to help you that has dealt with TBs from the track would be a great benefit.