My problem with the chain analogy is this: have you ever tried to push a chain? Don't work.
Catenary arch is lovely, describes the arch of my foot perhaps - but you are missing the point of balanced tension and compression - in a vertical pole tied down with three or four lines for example. That's a better description of what makes us stand up - look at this picture: http://wwwhome.cs.utwente.nl/~jagers...tensegrity.jpg
btw - having a great time with this.dk