How much would the aerodynamics of the car be disturbed, if you went with the front bumper but not the rear wing. Porsche recommends not doing just the bumper. Is that due only to aerodynamics or some financial cause?

And does anyone know the difference in clearance?

 

Many years ago Porsche used to not recommend one without the other. I can't say if that is still the case today. They do their aerowork with them together, so they can't guarantee what stability issues you may unearth by just doing the front. I can't imagine that doing the front only would cause much trouble. It might reduce some air beneath the car and the factory stock tail will help kill the lift in the rear anyway.

dan