I'm building a track day car. I really don't have any rules to abide other then safety.

But things change.

So I am wondering, I have seen rules that reference no rear aero devices (wings/spoilers/etc ) can extend past the rear of the OEM car, I think is good summation of the intent. It makes sense and seems fair.

My question is, has anybody dealt with this, and does it it mean past the farthest most point of a car, or cannot extend past any rear point of a cars rear outline?

My case, I have an angled rear bumper, where do I reference to?

The location of a wing is greatly effected by how close it is to a horizontal surface, and as far rearward as possible is best for many reasons.