Here is the recommendation so far, based on reading where people are experiencing road rash:
Full front bumper, carbon lower lip (front splitter), head lights, full hood, full front fenders, full doors (factory piece below doors is not enough) full turning vanes and the painted area inside, full rockers behind doors, and either full rear bumper or a good section running behind rear tires down to the bottom corner of the bumper. Would also do the windshield, not too bad at $350-$500, much cheaper than a new windshield.
Keep in mind that the newer nano self healing films will help, but if you like to tailgate or drive next to trucks instead of passing them quickly, a big rock hit will still go right through the film.
Basically optimum would be everything except the roof and rear hatch. Could do the rear spoiler / air brake, but will not be doing that on my car.