I think the best part about this are the colors and the range of edge relationships. I like the way you treated the hair as a mass, and the shifts in coloration are very pleasing. I tend to focus more on color than anything else in my paintings, so I'm probably your ideal audience. :3
The anatomy is close, but feels a bit awkward, similar to the other large drawing of the man lying down (though maybe not as much), but that just gets down to more careful observation; I know the figure gets exponentially harder the bigger you go, so I don't really fault you on this (I have a painting I made this semester with a shrunken head :/). I'd just say make sure you're stepping back from the work more frequently, especially in the beginning stages when you're laying out the masses. Looking at it in reverse helps too (mirror).
Anyway, it's really great to see someone dedicated to accuracy. I'd love to see this in person.