As per the original request about headlight tints, I did it and noticed very little loss in light output from my halogens. So little that I don't see it as an issue at all.

Here is a picture from this past saturday:

 

IF you use electrical tape... the Scotch 33+ has a great adhesive, doesn't goo up, and lasts forever. Had it as body trim tape on an older VW Cabrio, put it on and it lasted 2 years, no problems, just washed it when I washed the car.

Blackout tape works best on grilles, or use the carbon-fiber tape (that looks great too).