On Apr 10, 10:52 pm, Bruce wrote:
Weight and size. (you did ask)

I did. :-)

Weight: Hopefully Cui's battery improvements (or some similar change)
will alleviate the need to carry many pounds of batteries.

Size: Have you seen how small a powerful brushless electric motor is
these days? The prop has a large dimension in one direction; but at
least it can lie parallel to the mast and not take up much total
volume. I'm surprised there hasn't been more work on a ducted fan
solution - maybe the blades would just have to be too short to be
efficient, and still fit inside the aft fuselage... *shrug*

Take care,

--Noel