i went back and saw "ducktail" style and I have seen some photoshoped notches with a lil ducktail on it and it looked alright, very "car of yesterday" nascar-ish.
Ducktails are about the only spoilers worth having on a notch, period ... although I dunno of anyone that sells 'em. Thought about rigging one up, myself, but I don't have a large enough piece of sheetmetal to even begin...
It's definately noticable imo. It actually wraps around the front and goes down the sides a bit. Much better aerodynamicly from the looks of it. If you put it right at the front though, then it wouldn't draw air in to the radiator the same way.