They way i have written this hack is VERY SIMPLE. It works simply by creating a new Category for Private Boards. After you do this, there is a few small edits to Ultimate.cgi to filter out any board in the "Private Boards" category from showing up when displaying the main page. The second page is a duplicate of Ultimate.cgi, edited so that ONLY forums in the "Private Boards" category are displayed, then the duplicate is renamed "PrivateBoards.cgi".
I wrote this the shortest possible way i could think of, it is what i like to call a poor mans hack, no heavy tricks or code that you can't understand.
demo:
http://www.gamespecs.com/cgi-gamespecs/Ultimate.cgi PhOeNiX LanDinG