Two summers ago my good friend put his Renault R5 (Le Car) autocross car on it's roof. Pictures taken during the incident revealed that at one point a good portion of his arm was out the window!
Needless to say, anyone that is loony enough to autocross a Renault is also loony enough to rebuild it after rolling it. He basically took a good roof and hood off of another car, and had a unibody specialist replace the crushed bits on his car. We also cut the fenders and added flares to allow for much wider (13x8) Keizer aluminum wheels with big fat stickies on them. Oh, and he lowered the whole car like two inches. That ought to bring the CoG down a little!
I'll try to find my pics of the car post-accident. It's truly awful. The only thing worse was the 2+ hour drive home in his truck after the incident....