I have a non-elastic breastcollar that I am trying on my horse. He is shaped so that he has large shoulders, high withers, and a flat barrel which contribute to his saddle and girth sliding back. The breastcollar is all leather with a neckstrap and is designed to loop around the girth (as opposed to attaching to the saddle dees).

My questions are as follows:

1. How do I know if I've adjusted it properly?
2. How snug should it be when I first tack up?
3. How do I know if it is sitting in the correct spot?
4. Can I jump in an all leather breastcollar?
5. When I use it with my dressage saddle (short girth) should it loop around one or both billets?

I've never used a breastcollar before--just the standard hunt breastplates but those tend to put too much pressure between his front legs and across his sternum as the girth slides back.