Some other techniques you could also try -

See this previous post for making something with dimples in it, you may be able to adapt that for what you need:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2983.1


You could also try surface control point manipulation:
http://localhost/forum/index.php?webtag=MOI&msg=863.2


Also that kind of tensile surface is also called a "minimal surface", you may be able to find some specialized tools that are focused on producing that kind of thing.

Here's a couple:
http://www.susqu.edu/brakke/evolver/evolver.html
http://www.ixcube.com/dettagli.asp?n=20


Another possibility would be an animation program that has a physics simulator in it, for example Maya has a cloth module where you can make a mesh sheet behave like cloth and actually drop it on top of some poles.


- Michael