Putting a line on a car

How do you put a paint line from the front bumper to the rear bumper on any car? I would like it where you can type in any number, like 55 for example, to paint a line at 55% of the car's total width.

 

You have to make a skin, I can do it, tell if you want me to make a skin.

 

Hi. I really don't want to trouble you with that because I want EVERY car and to have this "feature" I want. Thanks though. Is there no way besides a skin?

 

Hi again. Is there a way for the game to show you where a percent of the cars width is without drawing a line? I would just look at the line, then just use my eyes to remember where that line was.