[Zope] How-to develop a folderish product?

Hello, I've just studied the "Python Product Development Tutorial" (http://www.zope.org/Members/hathawsh/PythonProductTutorial). This shows how to develop a Python-based product with a non-folderish object. I've managed to develop mij own non-folderish object this way. Now I'd like to learn how to develop a folderish object (again, Python-based). Can someone please provide some guidance? Is there a how-to/tutorial for folderish products as well? Or is it not that different? A practical question about folderish objects: Should it inherit from Folder or ObjectManager directly? Should it still inherit from OFS.SimpleItem.(Simple)Item? TIA, René Pijlman