What's interesting to me is that nobody in that thread actually used a sphere the size that Bucky proposed.

A sphere with a 1km diameter has a volume of 680,317,581 cubic yards.

A sphere 1 mile in diameter has a volume of 2,854,543,238 cubic yards.

The driving mass force per those comments seems to be the surface area of the sphere, which grows according to the square, but the lifting power grows by the cube.

I think this is legitimately the first time in my life, that I've considered the squared/cubed law as a bonus.