I personally have not seen 225's on any Contour or Mystique, but some peeps here on this board claim no problem with them. It just seems to me they are a little too wide and the center of the tire may stick out a little enough to cause the center to wear down alot faster than the edges. And I dunno, but if I spend $100+ per tire on a set, then last thing I want is a tire that will only last me 15-20K miles!
Again, I would recommend 215/55/16. Best fit and ride comfort.