[Zope] number of objects in ZooDB

Hi list, I use ZooDB to store a fairly large amount (?) of objects and I am wondering if it is best from a performance point of view to have a lot of small object or fewer bigger. About 75% of my objects are also cataloged in the Zcatalog. I have complete flexibility on chosing the object number/size ratio, as they are actualli xml fragments. My Zope instance is cached by a front-end apache and the objects are mainly read-only (apart from the initial import in the ZooDB). Is 500.000 objects to be considered an "high" number? Thanks in advance for any insight. __peppo