The maxloggedin template
should have a templatesetid of -2. I also don't know what difference it will make, but that's how it is by default.
I think the problem you all are having is because the index.php file in this hack is missing this:
PHP Code:
$loadbirthdays=1;
$loadmaxusers=1;
This needs to be near the top of index.php, just under the $templatesused bits. You'll see it's in vBulletin's own index.php. I've made a similar hack to this one, only I've never released it, and had the same problem with the maxonline record getting reset to the current number whenever someone loaded my home page. Putting those lines in fixed it. It's only the loadmaxusers line that you really need to fix this problem, but you should probably have the loadbirthdays line, too.