so, are production cars with flat underbodies just as susceptable to such backflipping? I know it'll be rare to be zooming along right behind someone at racing speeds, but could there be similar situations in other kinds of cars?

Not likely to happen in a production model. The front mounted engine keeps the weight forward, and makes it very difficult for the rear end to continue momentum under the heavier front end.

If you ever watch any kind of supercar racing you'll notice the racers will only draft off the opponent in front of them for a small amount of time. Most of the time they will only draft for a few seconds and pull to the side. This is better for the down-force of the car to keep it stuck to the road yet adds more wind resistance when there is no car directly in front. Just watch sometime and you'll notice this.
A great site to visit to know more about race car dynamics and aerodynamics
http://www.mulsannescorner.com/

While there are few production cars that can do a backflip, there was one French built car that was famous for its aerodynamics and producing enough lift at 35 mph to lift off the ground.
Other production cars can also produce lift and is noticable at higher speeds, but this affects handling around corners and stability at high speeds. Those oversized spoilers on Civics, Mustangs and so on are perfect wings for generating lift.

Dont want to be in one of those cars when they do their back flip