Hiding a specific forum from WOL

[NovoCiv]

I've been searching these forums and trying a bunch of things, but I can't seem to find a solution.

I have a specific forum which forces an Anonymous stylesheet so users can post in secrecy. However, it's easy for someone to look at a profile or the Who's Online list and see when someone is browsing the forum or even creating a thread. I could disable Who's Online completely, but I want to simply block that forum from showing up. So any time a user is doing something in that forum, their location would be shown as viewing Index.

Here are the approaches I've tried:
Template edits using variations of:

<vb:if condition="in_array($foruminfo[forumid],array(448,471,503))">

Messing with the session.location switch in online.php.

Plugin at online_location_process that attempts to change $userinfo['where'] to Index.

I haven't been able to make any of these work. What can I do?