Just wanted to pop in and say, from what I know, Chance doesn't look hollow in that video. Obviously not "collected", but y'all have covered that. I think with some more impulsion (which I know you're working on), she'll start learning how to use herself even better.
Keep it up! I'm starting down this road myself, and yup, it'll take a long time, but I'm already seeing improvements in Zeus on the lunge and under saddle, and we've only been at it for a month or so. :]
I give myself very good advice, But I very seldom follow it