Hi Peter
I find wire spiders are very strong, light and have little diffraction. I like the ones where the wires crossover like Mel Bartels uses on his scopes:
http://www.bbastrodesigns.com/ZipDob/ZipDob.html
Scroll down the page and you will see some pictures and a description.
For the hub I have been reading this page:
http://www.reinervogel.net/index_e.h.../3_MBox_e.html
I like Reiner's idea of removing the central bolt completely.
Hope that gives you some ideas.
Rod