Playing around with light groups in povray

I'm trying to get a comic book look in feel for povray. I want shadows on the ground, an otherwise flat color out to infinity (for a plane), and a three-lights system for the characters. It's a tough bill. I thought I had a perfect way to do it using not only light groups but a two-component floor. I had one floor of a few hundred units wide with default ambient and 0.001 units below it a plane with finish {ambient rgb 1}. So far I've failed.