I'm not sure how popular this module is with the wider Drupal community, but I prefer to use node_form_cols on all D6 projects to provide tighter control over where various fields and system fieldsets should appear on node forms. Unlike most fieldsets that are added by core and contributed modules, the "URL Redirects" fieldset does not appear on the "Manage Fields" tab and thus cannot be manually moved or (more importantly) hidden on specific content types.

I'm not sure what needs to be done to support whatever node_form_cols does behind the scenes. I'd be happy to provide more information or explain this issue further if it would be helpful. Thanks!