The reason my partner, the guuruu himself, was saying we might be able to fit an 8" wheel, is because of the smaller diameter spring that a true coilover kit would use.
A standard spring is typically 4.0" in diameter and GC's or true CO's are 2.5" springs. That means you have an extra 0.75" radius of clearance when moving to the 2.5".
Now to take advantage of this extra space you will require that same wheel, but wider, in a higher offset so that it will push that wheel inside the fender more.
I'm sure if you got a +50 on an 8" width and possibly rolled your fenders slightly you could fit an 8" without any problems. It would be close though, and considering 225 is the widest you'd go, I'd suggest just staying with a 7.5", as the extra weight in material will not serve much of an advantage.
If you go FI though, you might want to oversize the O.D. on the tire as to lower your final drive gear ratio to balance with the surge of added power.
It is a fact that the diameter of the wheel will make no difference as to what can or can't be run. These are totally dependent on the width of the wheel and the associated offset that the wheel has.
Hope this helps a little,
Rishie
THE REASON PEOPLE RUB WHEN THEY LOWER THEIR CARS IS CAUSE THEY DON'T LISTEN TO ME. ALL MP5 OWNERS NEED MY SPECIAL OFFSET RECIPE. THe one given to you by SEction8 above. I guarantee it. Plus you can run a 215, instead of that pussy 205 Honda s***. hehe.