Brasso brand brass polish can be used to polish out scratches in clear plastics. It states this use on the can, and I've actually used it to polish out scratches in plastic watch crystals and CDs and DVDs. Try that in a small area and see how it does with the cloudy canopy. Another thing I've heard is that pledge can be used to clear up cloudy canopies. I assume the wax fills in the clouded area and helps to clear it up.