[skyking]

Cool! Thanks so much for taking a hard look at it.

A moving floor becomes useful below 5" of ground clearance. At 13", it's more free air, than ground proximity. If the under body is rough, then it may be of benefit to drop the car, and force more air over the body. If the under body is smooth, it's more beneficial to have higher ground clearance. It's a trade off that's best explored in a wind tunnel.

1) Keep in mind that the real world still uses tires and wheels, and the farther you lift a body up the more the wheel frontal area and disturbance of the rotating disc come into play. There is no practical solution for fairing in the steering axle in particular, unless you have the budget of a race car company.
2) there is virtually always a crosswind component. A shape that kicks butt straight down the road will lose to one that is tested at a 1~3 degree crab angle, because that angle is reality.
3) #2 affects #3 as well. A disturbance from the wheel, projected across the underbody at an angle may really toss a wrench in the works, so to speak.