I find it was tricky to get the really dark shadows like you can in Poser. 

Using short ranges and high falloffs (range and angular) with the shadows all the way up to 100% gives you darker shadows.

I put up a freebie light set that renders pretty dark shadows here:

http://www.sharecg.com/v/28074/material-and-shader/V4-Skin-Shader-kit-and-Lights-for-Carrara-6

Any suggestions and improvements always appreciated :)  But I hope it helps you render the shadows you want.

:smooch:

Indi.