Brief follow-up for those interested in putting mud flaps on their Spark EV. emv ended up deciding not to install these on his car, so I bought them from him (the ones linked on ebay) and tried it out. The rears are way off, and would take a lot of modifying and carving to fit..enough modifications, that you'd probably be better off with some generic flat stuff. The fronts weren't too far off, so I made it work quick and dirty before my first hill climb to reduce the amount of gravel potentially flying down the side of the car.
The front mud flaps are made to have three screws attach them, two on the front face (facing the tire) and one on the bottom (facing the ground). The holes are not in the correct spots on our car as the Spark EV has the side skirts that are not standard on normal Sparks. No worries, as all I had to do was drill two new holes into the mud flaps and reuse the existing screws for the two forward facing screws (while ignoring the bottom screw, which isn't as easy). This was as simple as removing the two screws I wanted to reuse, holding the mudflap in the position I wanted them, marking a hole of the approximate location of where the screw goes, and drilling it out to accept the existing screw. These tiny plastic screws don't take much torque at all, so don't torque them down hard! This is what it looked like after installed:
I have had them on for several hundred miles, including plenty of hillclimbing and autocrossing, a couple of high speed runs, and a few runs through a grass field, and the mud flaps don't seem any worse for wear. Despite only using two screws (instead of the preferred three) they haven't come loose, made any funny noises, or caused any issues otherwise that I have noticed. The fit is quite nice, and at first glance you'd never suspect that they were not factory installed. I haven't done any scientific comparison testing to determine the affect on range, but I suspect this would hurt aerodynamics (and thus reduce range). You can see they catch quite a bit of debris!
Hopefully this helps if anybody else is interested in some factory fit-appearing mud flaps.
Bryce