[Zope-CMF] Compound type with External Image

[Ben]

I have a Portal product that creates a compound folderish type ( a Feature
Story) that can contain an arbitrary number of External Image objects.

My Feature Story class subclasses ObjectManager and Portal document, and in
it I have a wrapper to manage_addExtImage. When I try and add an image,
everything seems to go smoothly and the file is created in the ExtImage
repository but the object does not show up in the ZMI.

If I add an image through the ZMI within an instance of my class, it shows
up fine.

Any ideas what I might be doing wrong?

cheers
Ben