I shall move it for you now sir !
Not sure about the increase in sidewall profile, obviously the speedo will be out a little, may have some issues with diffs ? It's not something that's really done here in uk, if you want to do more serious off road stuff you buy a landrover or something weird,
Mr b's probably your best bet to answer your question, failing that have you looked over on www.forester.org or www.dirtyimpreza.com