betasniper -- Thanks, and thanks for naming them so they sort above all the deprecated versions alphabetically.
Xist -- I'm up late and the DHS is going to start categorizing me as a loon. I understood the question, too; see my response to aerohead, I just responded to one specific part. Since I posted I've been on Craigslist pricing rowboats.
Goodwill surfboards. Or an oval cut out of barn boards? I thought about clear plastic, but isn't a go-kart sort of a fairweather vehicle? I said trampoline net, but it should be a mesh that slows the air to ~1/10th velocity. At 60mph a rectangle would have a 6mph breeze front to back, an oval might have localized recirculation at the front or back.
Sorry, I see I'm mis-spelling 'Tropfenwagen'.