I'm not sure why, but I get the impression that the posterior stretches too far...I mean it seems anatomically correct but at a distance I just get that impression from looking at it.
Wait, I just got it. The start of the posterior from the back IS too high. I just used my body as an example by looking in the mirror. The waist begins at the bottom of the third set of abdomincal muscles, not the second. And at the top of the fourth set that strecthes into the pelvis, not the third. Take off ur shirt and look in the mirror, you'll see what I mean.
At least it works for me.
Aside from that small alteration...its an excellent model. Keep it up.