[pzs]

It would make an already dangerous sport even more dangerous. Also, just because it may be theoretically possible it doesn't mean it is practically achievable. Think about what would happen if the driver can't approach the loop that turns the car upside down with enough speed, or within the angle range that's needed for the car to stay on it because of another car, or some problem... Basically any small mistake would be fatal.

[bscphil]

Seems like some would have done it as a stunt at least, for sure. I agree with you that having it in an actual race would be infeasible.