Ae86 Wind Tunnel Test.....

[NoHachi]

Kudos for going ahead and trying your own experiments

Couple of remarks:
If your scale model is 1/10th the size of the real car, and you're using air as your medium, then flow velocities would have to be 10 times higher then the flow velocity of the real car you're trying to model. This is on account of something called the Reynolds number (do a wiki search if you're curious)

Aka modelling airstream around a car at 60+mph requires a 600+mph airstream round your model. Judging from your vid, you have a good estimate of your car at parking lot speeds

If you want to do simple grass roots research, a couple of things that would be interesting are:

Coast down tests. Measure the time it takes to coast down from a constant speed A to speed B. The faster you go, the bigger the aero influence will be and the better the results. Compare wing vs no wing to get an estimate of the added aero drag. Real simple to do. You could also do the reverse with accelerations.

There are also ways to practically measure the aero download. What you'd have to do is drive the car as fast as is legal for you. At a constant speed measure the deflection of the rear springs.
The expensive way to do this is with big buck linear potentiometers. The easier way would be to aim one of those key chain cameras onto your panhard rod and keep track of its angle. Less stiff springs probably help in letting you see anything. The car should sag more into its springs at speed or possibly lift less out of them.

My guess would be that it probably doesn't do that much for the overal aerodynamics. But would be cool to see someone quantify things.