I'm only one inch taller than you, actually. Does that make me "petite" as well? :-)
I'm naturally slim, but I do lift weights and like to develop muscle, because I don't want this hobby to cause me to become weaker. I'm not aiming to become a bodybuilder or anything like that, but the truth is, I know a lot of girls that have developed muscles but still manage to look quite feminine. So I feel that should be possible for a crossdresser as well. What I need to do more is pay more attention to stretching, because that's something I've always neglected in my workouts. Do you do a special kind of workout for your bottom?