Chris -
I can't find that hill either,
.
If you had a ScanGauge, you could do what Peakster did for an Acetone test, a point-to-point test on the highway :
Fuel Economy Test #5: ACETONE REVEALED!!!
In the meantime, here is a compromise version of the same kind of test I was describing :
1 - Find a long flat road you can drive at the 45 MPH or greater speed limit. I think you want to start with at least 45 MPH in order to focus on the effect of aerodynamic drag. The middle of no-where with at least two lanes in each direction is your best bet.
2 - Drive up to the speed limit and pop it in neutral at a specific point along the road. You can use a landmark and/or a pal on the side of the road to help.
3 - Coast down to a rolling stop as many times as it takes to get a reliable average for distance and time. Again, the idea is to show repeatability.
If the skirts work, both of those variables should be greater than without the skirts.
Having another pal in the car with a stopwatch, pad, and paper to help record the numbers would help too.
I don't like this version because it introduces human error at the point where you pop it into neutral. For that reason, I would predict that your "coast to stop" positions could be wildly different. The downhill approach lets good ol' gravity give it the exact same push every time.
CarloSW2