Anyway, I took the bike for a half mile test ride yesterday, and the Deraileur Guard clears my ankle. It does NOT interfere with pedaling . It clears the chain in all gears on the rear cluster. However, I did not try it with the chain on the largest Chain Ring. Again , the guard is a half inch thick, so it looks like it will clear, from the outside, but I'm not sure about the inside. I have to test ride it again in the big ring. I may have to cut, grind, or file a groove into the material, if it rubs the chain.
Those NuVinci Hubs look interesting, but they must weigh a lot with those huge ball bearings.