I was just out looking at the rear wheels on the prius. I don't know if there is enough room to mount skirts on it. I will try working something out with fiberglass molds and see if I can slide it into the space. It will have to come out somewhat just to clear the tire.
I'd love to see what mpg the Prius could get if someone did the full gamut of aero mods to it (like I did on my car). It wouldn't have much effect on those low speed drives where careful Prius drivers traditionally get their high mileages , but it would extend that high mileage envelope to higher speeds and would make a world of difference at 55 to 70mph on the interstate.
O.K. I have a new prius. I don't think that I am going to go as far as you have. I see a SC plates on that car. I live in Charleston. Are you anywhere close? I do have one question. How do you get gas into it? I see the gas cover was sealed closed.
I think any time you add surface area, it is darn hard to get an overall positive effect. You have to somehow decrease the effective Cd of some other aspect of the car to offset the increase in area.
I would think the belly pan is almost always a win situation. The air dam however, is trickier.... if the air dam does not increase surface area and simply redirects air away from underside surface collision, then its a plus, but when it starts dropping below and adding surface profile... that is tougher. Not impossible, but tougher.
Now lowering the whole car... that is another matter.
I also think twice about anything showing up on a racing car as lowering Cd is not their priority. Instead it is reducing lift, which an air dam does nicely.