[Logician]

Why dont you just apply some conditionals to the line?

PHP Code:

$ipermcache["$forumperm[forumid]"] = $forumperm; 


eg.

PHP Code:

if ($bbuserinfo[usergroupid]==X AND $forumperm[forumid]==Y)
{
// your custom permissions here..
}
else
{
$ipermcache["$forumperm[forumid]"] = $forumperm;
} 


BTW. IMO this hack looks pointless. You can really do it inside Admin CP just like you have mentioned. Besides this method will only make sure the forum is not visible in the home page, but users will still be able to access them via Jump Menu, User CP or Search page..

Unless this is what you want in the first place..