Curious about the details of coast down. Would the test area need to be flat? I guess it's theoretically possible to account for dips by using a vehicle with a known Cd to calibrate the test road, but that sounds hard. Any factors that wouldn't be consistent would need to be eliminated (like bumps). Probably a lot less frost heave in South Carolina.
Getting the timing and speed info doesn't seem insurmountable. You'd need some of those switch cables (or whatever they're called) that you see used to measure traffic density and speed. I guess a light beam setup could be used too.
: a psychological condition or a relationship in which a person is controlled or manipulated by another who is affected with a pathological condition (as an addiction to alcohol or heroin) ; broadly : dependence on the needs of or control by another