Hold up! Before you make what I would call a backward move by going to inferior tires, I would suggest you simply try things like adding more rake to the car and you can change toe in and camber settings.
What you should be asking, imho, is 'who knows a really good shop in my area that will mess with my car and make it handle the way I want'.
Going back to smaller tires with flexible sidewalls will give you wheelspin and less grip and less braking and lower cornering speeds.
These cars are highly adjustable. Even getting adjustable sway bars allows you to fine tune the car.
I love this website, and the guy that runs it to:
http://www.rennsportsystems.com/2b.html