Poser 4 shadows are awfull to work with, I'm far from really understanding them. The only things I know are that adjusting the shadow cams can help. Infinate lights seem to have a longer focal length on their shadow cams, which usually gives better shadows. The geometery in the doc has a lot to do with it, hence the trick of putting a square under the floor to solve the no ankle shadows problem. As a demonstration of the effect geometry can have on shadows see the graphic above, the only change made between the two images was the character, which was changed via the double tick marks at the bottom of the pallet, so she is in exactly the same position, and the same pose!