I actually did it with a 3000GT LM and with.....
Full Downforce - The car fly up in the air and landed on his nose, then it flipped and did the aformentioned "car breakdancing" and spinning......but it did so while staying up on the top of the corner...
Minimum Downforce - The spun out and went straight down to the grass and lasted about 1/4 of the length of what happened with Full DownForce.
The GT-One and R390's do some impressive flips and spins when you do the same thing.