Nice
About the anatomy:
The chest and stomach muscles aren't accurate -
I. you've got too many sets of muscles. There should be 3 pairs. 4together with the chest muscles...
II. the muscles are not defined in a circular pattern on the stomach but fade out while they stretch around the ribs.
III. The top set of stomach muscles is directly beneath the chest muscles. There is an area around the sternum that's a bit weird and varies from person to person.
This is based on my muscles but I'm pretty sure that's accurate anatomically...
Benny

BTW, the area where the mask ends doesn't look so convincing... You might want to check it out