[Zope] module shared between products

I am developing a project which I have split into two products to avoid having too many files in one place. I want to use a common base class in each but I can't find out to do this while keeping all three product directories together. There is something about multiple product directories the archives: " If you are prepared to edit Products/__init__.py add a line: __path__.append('yourpathhere') " Is there a simpler way to do this? david