I'm not interested in beating a dead horse, again. The how fast will a C3 go has brought up a ton of great info. Some we will need here.

Somehow I found a "Hypermiler" mpg forum. They have a section on Aeros. I was surprised at how much was gained by smoothing out the trailing air off the rear of the vehicle. They didn't use spoilers or wings.
They had these long tapered rear ends that extended the rear a few feet!
The front air dams they used were just sheetmetal or cardboard w/bracing. They were getting more mpg out of the mods to the rear of the vehicle.
To be honest, the air dams were weak. The front end aeros of these econo cars are also not aero friendly, but they work. They were testing at Hwy speeds on the flat. In their world merging, passing and hills don't happen, so extra power is not being lusted after. lol
It is said that the PC kit improved aeros 15%. That is on the fastback which has to be smoother than the earlier C3s.
I believe that it was caculated on "How fast C3" that it takes 350 rwhp to go 150 mph. I am sure I will be corrected if wrong. NO PROBLEM!
W/150 mph as the goal-

What if: The air dam and rear spoiler on the PC were doubled in size and
the angle of attack was halved? Would that decrease Cd and maintain downforce, or would it improve both Cd and downforce?
I want the look of the PC aeros, but doubled I'm afraid would be too much Cd and more downforce isn't needed for my plans. Less angle on both should help w/Cd. Any thoughts?
There was a FB that had a very flat rear spoiler that surrounded the rear end. That's what I'm thinking of. TIA

R
I wonder how much side mirrors hurt?
Does this make sense?