[im3w1l]

I did check the wiki article on Vacuum airships before writing my initial comment, and they are talking about the buckling of a hollow sphere, not of a column - hence why Akhmeteli and Gavrilin suggest considering alternative structures.

But regarding your point that the columns would have to scale with volume you might be right about that. I was thinking that it should scale with the total force, but the bigger your structure the longer distance the force has to be transmitted. So yeah I think I got that one wrong.