[Zope] Multiple site deployment

The project I'm doing will be deployed to several intranet sites. I'm developing content and logic in dtml plus a few external methods. Each site deployment will be customized. The customization is simple: basically changing the standard_html_header, smtp server name, and things like that. Dealing with software updates can be somewhat of a problem since I'll have to recustomize every data.fs before deployment? How are other developers handling this kind of customization problems? The Directory View from CMF looks to be useful in storing some of the customized dtml in the file system. I've tried ExtFile but it doesn't have external dtml documents. Has anyone used zope with configuration files before? Chui