Way fucking awesome!!

I think that you've got the panty shot thing down. :)

The perspective in the back arm needs some work... it also almost looks like its totally off her body. The size of her head makes me think it should be closer to her head. Also I would recommend grounding these girls. As it is they are just floating in the air. Try putting a shadow underneath them or a horizon of some sort.

Keep it up. :)

Good Stuff! I really like the simplicity of it. I like how clear the lines are and the shading. Everything is crisp yet you don't lack depth. Nice Job! The only thing that I would have liked to see was a little more of a background. However really nicely done.