Wow..this thread helped. Awesome thread on the "gather" nod. And I had it the other way around when it came to receiving, transmitting light and couldn't succeed. 

This image, I used gather nod (Floor, walls..except for the wall on the right of image) and two infinites, to light outside of this MechHanger building in helping bring light into a room. This render took two hours, and was worth it in learning how to use this nod. Wonder if P7 is better on the "gather" nod or both P6, P7 the same?