Planning on rolling the rears, and maybe even flaring them out, BMW style, like DieselX did with his rears...

 

Guys I am running a 20x8.5 +40 with a 15 up front, and a 20x8.5 +40 with a 10mm spacer in the rear. Yes I had to roll the rear fender but that is pretty much it. When I had the 15 spacer in the rear, I rubbed on hard bumps and when I had a full car, so that is why I switched them up. So I think with a 20mm it will be ok, but yes with a fender roll.