Many of you are aware that Stig's Camaro started on fire resulting in a total loss driving down the street. The lining in a motorcycle rated brain bucket is not fire retardant. It is all good until something goes wrong and the only reason you wear a helmet is for when something goes wrong.
The ONLY reason tracks let you run a car with a M helmet is you have signed away all your rights to sue. If you get hurt you are on your own. It has nothing to do with your safety.
A Well driven stock 5TH Gen runs damn fast on a road course. Gingerman is a very forgiving track with the exception of the last turn off the back straight. Everyone should end the day without incident. As many times as I have never seen a driver require medical attention. There have been fatal accidents... until things go wrong.
We have gone round and round about this for years regarding CamaroCross. If the decision were mine SA rated helmets would be required. Your brain is what you are. It deserves to be in the best helmet you can afford. Helmets come before mods, drinks, dinner... You get the idea. This is my opinion and nothing more. Take it for what you feel it is worth.