@melikia

I got round to doing a couple of experiments (in V5i - can't afford the upgrade to V6)..and found a major omission in your settings as shown at the start of the thread..
You need to check "Cast Shadows" (top right of the edit panel) for the light to create the fullest effect. Also 1 sided/2 sided makes no difference.

Cheers,
Diolma