This is something I have had trouble with riding my Fox Trotter too. I am used to "collecting" and tucking the head of most horses I ride, at least at any gait faster than a walk (at a walk I always prefer a loose rein).
So now I have a Fox Trotter ex-broodmare, who does gait really nice when she wants too, but she also trots roughly if you let her! My natural inclination is to try to tuck the head and I know NOT to do that with her, but gosh, I am not very good at bringing out her best gaits either!
I have a hard time accepting that the head is suposed to be up and the nose is supposed to be out, lol! And a hard time knowing when I am doing it correctly. I feel like I am hollowing out her back if I let her head to come up.
How do I know if her back is too hollow or just right? I guess if I get a gait I like? She does gait better with a higher head. I just don't know when a high head is correct and when I am hollowing them out. I actually wouldn't care if her back was hollow other than people act like that is really bad for them.