[07b2300]

I'm considering a grille block and have read lots of threads but can't find definitive answers on these questions:

1) Does it make a difference if a grille block is in front of or behind the grille? I read that a stagnant air bubble would form in front of the block like the the "tailgate up" mythbusters that found tailgates hold stagnant air in a truck's bed that helps aerodynamics. A grille block would obviously look better behind the grille and emblem and I would rather do that.

2) Does blocking the top grille or the lower bumper grille work better for aerodynamics and/or engine cooling (assuming both are the same size)?