i want to install a pair of round driving/fog lights in the LOWER grille of my 04 Cooper S. Has anyone done this and how does it affect cooling?

 

I've seen it done. Someone posted pics of theirs on here or Mini2 a while back. Don't know what the final analysis was as far as cooling goes. Since the other parts of the lower grill aren't cutout I don't see that there'd be a problem as long as you mounted the lights in front of these areas.