Careful, you can read adventures of Imreza and WRX guys running their car for RWD fun for hoonage or autocross. The rear axels and diffs on those guys weren't really designed for that sort of thing and have been known to break if run very long or abused under those circumstances.
I've never done it before but I've read about it, you'll want to ask around on some Subaru owners groups forums if you're really going to give it a shot. Then again be prepared to catch a lot of flack for wanting to change one of the main features that makes it a Subaru, those guys can be rabid.
