I never really lunged any of my horses before execpt for a quick spin to relax my green brokes before riding. But now lungeing is all I can really do with my 29 yr old mare who foundered 2 years ago b/c she's forever off on her front right. So....I started lunging with my bridle and a snap on convertor...what is the best bit to use? I'm thinking snaffle. Opinions?