Her ass looks strange because the view is not in proportion which the rest of the picture. I understand you probably didn't want to give her a huge ass which is understandable but even so its not quite natural to have an ass that small with thighs that huge. xD Aside from that this drawing is an excellent reference, as well as a great guide.
Heh, thanks I'm a little suprised people like the hair so much, it isn't even really done. At least like i'd like it... Anyways, about the top... Hmm... I guess you're right about that XD I'll keep it in mind.