[M_a_t_t]

The only thing I've noticed with my car (not really that aero actually) is that it gets shaken very easily. If I'm behind a pickup or full size van at speed I can feel as I enter the turbulent wake, its not subtle either, and seems to have gotten worse after I put my tail on. The car is only ~2300 lbs though so being light(er) definitely affects it.

Theoretical talk though there is too many variables. Just like if you simply ask if xxx will improve on my XXXX car, you can't really apply general rules and expect great results (mediocre-good at best). If it is built in a wind tunnel it will probably be planted on the road and be fine. If you do it like most of us do on this forum I think there is always a chance of making the car handle worse.

Maybe a question in a question: If your vehicle is already turbulent and you pull into a turbulent wake from a semi, will you feel it as much since your car was already in turbulence?