Hi Warren: Heyman literally "wrote the book": Heyman, J. The Stone Skeleton: Structural Engineering of Masonry Architecture. Cambridge University Press. 1995. Re tension: You are correct. Without some additional horizontal force somewhere, the erf/erg dome can't stand. Chains around the base are a cheap/easy solution to this problem. But the bulk of the dome is only in compression. ---- You might enjoy the "oil lamp" shaped constructions towards the end of the following paper. Curiously, they don't consider 3D constructions. Overhang Mike Paterson, Uri Zwick (Submitted on 12 Oct 2007) How far off the edge of the table can we reach by stacking $n$ identical, homogeneous, frictionless blocks of length 1? A classical solution achieves an overhang of $1/2 H_n$, where $H_n ~ \ln n$ is the $n$th harmonic number. This solution is widely believed to be optimal. We show, however, that it is, in fact, exponentially far from optimality by constructing simple $n$-block stacks that achieve an overhang of $c n^{1/3}$, for some constant $c>0$. http://arxiv.org/abs/0710.2357 At 08:19 AM 11/12/2012, Warren Smith wrote:

So I have a certain amount of skepticism Heyman knows what he is doing.