Looking underneath the Leaf, it's relatively smooth. Not nearly as aerodynamically "dirty" as my Yaris was, for certain. The rear bumper actually goes up smoothly into a rear diffuser instead of a big open parachute like the Yaris.
Up front are some flexible rubber wheel spats in front of the front tires. I think I can do better. I would just add material to drop them down closer to the ground and split the air more effectively, leaving these stock pieces in place.
It must be said that their placement (IE the angle and shape) is interesting, and makes me wonder if this was something designed in a wind tunnel--and therefore something to keep and just improve rather than deleting and remaking.
I also plan on purchasing either rain gutters or some other such material to make side skirts. No sense splitting the air if you don't give it somewhere to reattach.