You know what? I was thinking about doing this, since the black vinyl on mine is wrinkling and peeling off on both the spats just where the front of each meets the body. Not badly, it's an area roughly as wide as a quarter and maybe 1/16th inch deep, but it still bugs me.
My fear was that the one-color rear end would look "heavier," as the black slash goes a long ways towards streamlining the look of the rear end. It's a visual thing, but it's definitely noticeable. The rear end of the Insight... well, let's be kind here... it ain't no Auburn boat-tail when it comes to elegant rear ends... it's my least favorite angle of the car.
I think I'll have the car repainted this spring, but instead of using a vinyl applique, I'll have the same area
painted black. No more vinyl peeling...