Team Concert Database Sizing Guide

I'm pulling together estimates for an RTC implementation for a relatively large IT shop (300+ active developers). But I haven't been able to locate a database sizing guide to determine how much storage will be needed. Is this type of information available anywhere? It doesn't have to be exact but I don't want to have to acquire and install additional storage for the DB immediately after standing the environment up. We'll be using UDB 9.x on AIX.