[Zope-dev] Max objects before ZCatalog?

What is the magic number for performance? Between the individual lookup, doing a 'large catalog' ZCatalog search, and creating many ZCatalogs. I'm accessing a few variable (~ 2-8) in 20-5000 (~max) subobjects and testing them against the current objects variables. The design is for something that most scale and can easily to be changed (I have this half done). The idea is really close to ZTopics, with my own idea of a minimalistic custom implementation. Is there anyone who has experience or has done performance testing and would like to comment? Thanks in advanced, David