[Zope] restrict Add drop-down list in Folder Contents view

I have a Folder and I want to restrict the types of objects the managers of that folder can add to it. In the Security tab, I can limit the kinds of objects that can be added, and this works fine, but the forbidden objects still show up in the drop down list in the Contents view. I know I can create a ZClass derived from ObjectManager and just select the limited set of Subobjects, but this imposes extra overhead and a proliferation of specialized container ZClasses. I would really just like a Folder where the manager sees only the kinds of objects he has the permission to add in the 'Add' select list. Any suggestions on how I can do this? Thanks, John Hunter Zope 2.5.x