Lights behind grill?

I'm debating whether I want to put lights on a prerunner bumper up front or behind my grill. I'm thinking about Hella Black Magics which I believe are something like 3" deep. I'd rather put them behind the grill so I don't risk breaking them or getting them stolen off the bumper. I'm just curious as to whether this really affects light output or whether it poses problems in terms of clearance with radiator and such. I know I've seen a lot of trucks with lights behind the grill but alot of them are street queens - I'm actually gonna need these lights. By the way I have a billet grill. Input?