Looked into perforated vinyl. From what I understand there is a vinyl that can be used inside the glass. It would be easy for me because my car is black and they make black vinyl. I would like the vinyl inside so UV light doesn't make it fade. The glass would prevent that from happening. I could do the sides and back glass.
Will give you an update when I talk to a vinyl distributor/installer.

 

Honestly, on a black hhr the windows are dark enough I'm not sure it would change much.

 

Your correct. I went outside and looked at the car after I posted the idea and thought the same thing as you.
Well that was a science project that failed.

 

Don't worry, theres lots more where that came from Im sure.