[aerohead]

Best I can tell, the SAE still recommends :
1) a 16- degree 'approach' angle ahead of the front tires.
2) 10-degree 'breakover' angles behind the front tires, and ahead of the rear tires.
3) 10-degree 'departure' angle behind the rear tires.
--------------------------------------------------------------------------------------
4) If these angles are not respected, you run the risk of a ground strike and body damage.
-------------------------------------------------------------------------------------
5) 'Active' airdams were introduced in the early 70s by VOLVO on their VCC concept, and would be a 'workaround' for the front clearance.
6) 'Active' diffusers were introduced by GM in 1982 ( Aero 2000/ EPCOT concept ), and would be a 'workaround' for the rear.
7 If you're willing to take all driveway ramps at an oblique angle, you might be able to survive with a 'cheater' set of skirts or wheel fairings.
The 'template' illustrates a wheel fairing package ( or skirts ) which respects all SAE underbody clearance requirements.
PS, rubber belting would be able to survive ground strike and abrasion, although it would be subject to aeroelastic deformation.
PS-2 In the State of California, expect the Highway Patrol to pull you over if they see any part of your car lower than the bottom of the wheel rim.