Nice tester! Bold. Big gain to go with it. Design reminds me of the cardboard airdam I built with students as a proof of concept for them. We saw big gains too. Your design reminds me of the Insight at this year's "Green Grand Prix" ... here's a photo from that thread:
When you redesign maybe you might imitate this bolt pattern. But be aware. This low you are gonna scrape every dip and hit every parking block. I raised my airdam an inch or two to avoid that. It was a pain.
Great stuff though!