Curious why they decided to only put an apparently safety cage over part of the propellers, that's fine if you don't fall off and never wreck, but I could easily see a mishap exposing a limb to the unprotected region.
It's too bad he couldn't have an simply automatic grid at low speeds and once going the grid pulls or rotates out of the way for better efficiency.
Actually a rotating grid may work using the air as its triggering force, once the air speeds up some sort of venturi force enables/disables a safety mesh across the opening.
