I and a friend run 16x7 all around with 225/50. It's not the fastest setup, but it's still fast and predictable. The key is to add to the rear some 21mm 928 or 28mm 930 spacers with longer studs, to keep the rear track width at least as wide as the front.
Here's me chasing said friend at Blackhawk Farms- both of us on 4 16x7 with 225/50.
http://www.youtube.com/watch?v=QHYwvfPwxFk
I switched to 225/245 with 16x8/9 this year and friend was still hanging with me at that track- punk pulled 2 seconds out of his arse somewhere because I for certain improved my times!!!!
