Cropping Fixtures/Dominant Fixtures
Essentially I think you should be able to assign dominant fixtures that crop the grills in the case of headlights that have odd grills because they are placed on top of a grill.
To illustrate, here is an image of one of my affected designs:
http://postimg.org/image/a3x036sxp/
As you can see both headlights on either side are blacker (the extreme right and left ones have only half the grill behind them) and it looks pretty unpleasant.
Thank you for your consideration!