What a nice looking girl and how much fun you seem to have with her, awesome. I would recommend a joint supplement (Cosequin, Cetyl M; at her age, don't mess with untested crap) and keep her on her great turnout schedule to keep her going for many years. What kind of grain are you using (label specs)? I would imagine from the descriptions and the pics she doesn't need hay added in the summer:-) She looks so nice. As for building her topline a little...does she stretch down or hollow when you ride. Stretching down and lifting her back will help. I hesitate to suggest a lot of circles or ring schooling since you have such a nice balance of riding her in the open and that is much better for her joints at this age then lots of circles. (And this coming from a dressage queen...hahahaha!) Anyway, interested in your feed. Have a fun with her!!