proper offsets for 17x9's

[tard cart]

Picking up some wheels for the a4, and trying to figure out some offsets to make them flush or very minimal poke. They are et 41, and I can get 15mm spacers included. I think I can pull off the et26 in the rear, but thinking that will be too much in the front. Im assuming the stock et41 will rub on the inner fender, so what offset would be ideal? Any help greatly appreciated.

[tard cart]

Would also like to know if a 20mm on the rear would be overkill?