[Zope-CMF] how to override folder_contents action?

[marc lindahl]

I was making a Scriptable Type Info type, to allow making Product within the
CMF environ (ZopeGUD to be exact) and oddly, regardless of setting of 'use
default type information' when first adding it (what does that actually do,
anyway?), I get a folder icon when an instance is added (regardless of the
icon I tell it to use in it's portal_types properties), but the main thing
is,  in the actions menu, I get a 'Folder Contents' action which goes to
instance/folder_contents.  I've tried to define a folder_contents action in
the portal_types actions tab, by naming the id folder_contents (I figure the
name doesn't matter?), and the action my new action (for example,
index_html_alternate, or manage_edit, or whatever), and category either
object or folder, and permission a host of different things (access contents
information, modify portal contents, view...) nothing seems to override this
folder_contents method....  what am I missing???