Thanks for the help.
Here's my latest version.
http://www.singaporeanimenews.net/gm2.jpg http://www.singaporeanimenews.net/gm...ws.net/gm2.jpg
What I did was
1. blur the edges of the mask slightly to antialias it
2. add shadows below the chin and around the eyes
3. adjust the mask contrast with a curves layer
4. distort the mask with distort and perspective transforms to make it slightly taper towards the chin area
I think it looks a lot better than what I started with, but still doesn't seem quite right.