I think you're going to be pushing it in the back. It's also going to depend on what size tire though. Sweet wheel choice however. One of the wagon guys will know better than me and my delicious sedan fenders.
sedan fenders look bad unless you get rears molded into the doors(IMHO). I have 7.5x18 P1s on my car, my roomate has 8x18 P7s on his wagon. He was able to run 245 Yokos on his but it rubbed all the time. I've got 225s on mine and after having the camber adjusted correctly I have not had any issues. Both of us are on Prodrive rims, so the offset is Subaru specific. I don't remember the exact numbers though.
depending how low you are and how much negative camber you run, with an 8 inch wheel and a a 225 you'll need at least a +48 to be close to not rubbing and there's still a chance you will. break out a heat gun and baseball bat! i run a 7.5 with a 225 with a +48 offset lowered on s-techs and i get slight rubbage occasionally