Okay got around to drawing it.
How much effect would a window mounted spoiler like that help do you guys think? The length it extends back over the windshield will be limited by how much extra space there is in the softtop storage compartment :/
Could probably use a rear spoiler as drawn in the second image, I got the "curve" pretty wrong but the Spyder has very little length behind the passenger compartment and so the flow off the top probably never reattaches to the body, I'm guessing.