Folks,
Are the side skirts (probably the entire panel) different on the C4S than the C2S? Or just an additional piece of black plastic? Can I install them onto the C2S?

I know you can't do it for the rear red reflector bar across the bumper, the C4S bumper seems to have a slot for it. It looks nice though.

 

Hehehe I've seen this question posted before and didn't answer because I figured someone else would... no one did .
So here ya go, the side-skirts on the C4S are mounted on the bottom and follow the line/contour of the body.
Since the C2/S and C4/S don't have the same shape (between the doors and wheel arches) this means the skirts are not inter-changeable.

That said, there are more and more after-market side-skirts which will do a nice job but they "wrap around" the bottom edge rather than just being mounted below it...
Hope that helps.

Cheers!