Is there any recommendation for sizing z/OS DB2 tables for future growth of the repository?

My customer wants to know if there is any recommendation, based on IBM and other custormers experience, about sizing z/OS DB2 tables, not for installation and startup, but for future growth of the repository. My customer wants to size the tables in advance and not to be reactive when the repository grows due to adding project areas, streams, repository workspaces and so on.

I have not found any hint or recommendation about this in these articles:

RTC 3.0 sizing guide for z/OS:
http://jazz.net/library/LearnItem.jsp?href=content/articles/rtc/3.0/sizing-guide-z-os/index.html

RTC 3.0 performance tuning guide for z/OS:

https://jazz.net/library/article/622.

I know it is not easy to size this in advance, but ....

Any hint will be much appreciated,

M. Jose