That's the same aero lotus used in the 70s in f1. I been thinking of doing that on one of my supras one day as wellWOW! This is really coming along Josbeat.
On the Time Attack Forum http://www.timeattackforums.com/forums/aero-dynamics/4604-flat-floor-ideal-height-introduction-my-mk2-golf-aero.html, I read a build in the Aero section, where they added side skirts using angle aluminum and screwing on vinyl so that the air that is split at the front stays under there all the way to the diffuser. It is an interesting read. I'd like to hear your opinion on that set-up.