wheel backspacing on an A5 2009
 

Im new here I just recently purchased an 2009 A5 Quattro. Im wanting to put new wheels on it, 20" staggered, does anyone know what offsets I need to get to run a 20x9 in the front, and a 20x10.5 in the back or a 20x10. Im trying to get the wheels more flush with the fenders, so they don't sit in as far, I've done a little research but I would rather ask some experts around here who have really played with these cars. Any help is appreciated!

Alan