Restricting access to Standard Reports (folder security)

Summary

Advice on how to block access to the stadnard reports for some users.

Content

Let me start by saying I am familiar with the traditional folder security mechanisms.  (Creating a user group, putting users in the group, then going to OBI Folder Security in Configuration and selecting which folders each group can see.)

However, we would like to block access to the canned "Standard Reports" folder that comes with all the pre-built reports.  We would rather have our staff utilize only the custom reports we have put out in their role folders and not the pre-built reports.

When I go to folder security the tree only goes as high as "My Company Shared", so I can't seem to assign folder security to the Standard Reports folder.