I didn't get the chance to get many runs in with the wing on the car. The engine was just getting too tired and I pulled it to do a freshen up and some major upgrading to it.
The few runs that I did get in seemed to show some improvement, but I really didn't get enough runs to come to a solid conclusion.
A while ago, I did start on paneling the underside, and I will be building in a diffuser after the rear axle.