the windsplitter already has been coated with 1/8th inch of clear...
this is why it's shiney ... if it had no clear on it, you would get a dull finish and you would be able to feel the Carbon Fiber
Notice how the top has clear on it - and the bottom doesnt
if you are worried about the bottom.. just take black glass spraypaint and cover with several thin layers - but in reality, no one will ever be looking at the bottom of your car unless they are changing the oil
if you get scratches on the top, just buff them smooth again...