Hot answers tagged body
I like to refer to those as eyebrows, and in the specific image you posted, they are to add some stiffening and down force to the center of the bra so the flat edge against the hood doesn't flap around in the wind. Since there is nothing to fasten the center of the bra to, the designers had to resort to aerodynamic forces to keep it in place.
I would use epoxy primer to start. You can then spray paintable undercoat on your frame, underbody. They come in various forms as depicted in the image below. You may also use a rocker guard type product as shown. To my personal taste, I would seal with epoxy primer, rubberized undercoat, and then oil undercoating to protect even further. Application ...
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