I've had a look at the ProtoStar spiders and secondary cells too but decided against them. I'm looking instead at the goodies made by these people:
http://www.observatory.org/spiders.htm
and while they seem pretty expensive they look very well made.
For my purpose (a Cassegrain secondary, not a Newt), they win over Protostar.
I could not find AstroIndustries anywhere. Do you have a link?
Peter.