Trixie is 8 and is all go. I just got her and was using a medium port loose cheek bit on her to test her out. I found that she is very quick.. doesn't like to slow down a bit... and her mouth is VERY sensitive. She doesn't neck rein right now.. which I need to work on... but that's not a huge priority for me. Does anyone have a bit recommendation for a very sensitive mouth on a hyper, highstrung horse? If I did anything more than lightly touch her mouth, she started spinning like a top... not being ugly.. she was trying to follow what I was telling her.