vilters:
V4's back bending above seems fine to me, although I'm not an anatomy guru.  Backs vary from person to person, and sometimes they even crease (which I suppose Sydney can be let off the hook for):
http://www.globalyogasf.com/images/Ivy3.jpg
^^ yikes, bad creasing problem!!
http://www.limbermen.com/Piedra/an.JPG
^^ a flexy sexy man

I don't see the issue you're pointing out with the left V4's hip/thigh.  The right side V4 actually has her thigh bent at a shaper angle and I see no kink there either.

The chest bending wierdness I'm just going to blame on the "universal pose" that doesn't work well on either character, although imo V4's back and chest are visibly more resistant to kinks and creases.

Neither figure has perfect feet bending, although imo V4s ankles look a lot more realistic than the giant, meaty tendon with the huge kink in it illustrated above in clsteve's image.  On a human body, that tendon does not bend regardless of where the foot is.  The crease at the back of the heel is exaggerated by the by the lighting, it's not really that bad.  It isn't right, but it's unusual for it to show at all in my experience so far.
http://www.renderosity.com/mod/gallery/index.php?image_id=1343887

Sydney's upcrawling buttock is one of the most unappealing and unnatural thing's I've seen lately.

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