I would use a design based on this one:
Who makes this trailer hitch : 350z / 370z Discussion
I'd change it up slightly to compensate for the fog light assembly which interrupts what would be a smooth surface on the inside face of the bumper. I'd have a custom cut plate of steel that runs the along the inside face of the bumper with a cutaway for the fog light assembly. You could then use two of the down tubes whereas they only used one on the above link. If you wanted to go further, a forward running tube mounted just behind the diff would add more strength.
The best thing about this design is that you could take it off when not in use. That way no one would know you
fuked a fat chick had a hitch on a sports car.