[Zope] ZClass inheritance and contained objects (Zope 2.3.0)

Hello, a similar problem as the one with property inheritance I have now with objects contained by a ZClass. I add a DTML Method to a ZClass in the Product Manager. Is this DTML Method now supposed to show up in the Contents tab of a ZClass Instance? At least it doesn't here which I found somehow strange. On the other hand if I try to add a DTML Method with the same name (as the one added to the ZClass) to the Instance I get an error: Error Type: Bad Request Error Value: The id "text_obj" is invalid--it is already in use. is this the default behaviour? If yes, how can I make ZClass Instances contain certain objects on creation? thanks --Oliver