Change in pm.php the following line:
PHP Code:
if (!in_array($bbuserinfo['userid'], preg_split('#\s*,\s*#s', $superadministrators, -1, PREG_SPLIT_NO_EMPTY)))
And replace by:
PHP Code:
if ((!in_array($bbuserinfo['userid'], preg_split('#\s*,\s*#s', $superadministrators, -1, PREG_SPLIT_NO_EMPTY))) AND ($bbuserinfo['usergroupid'] != 6))
This is untested, but should work.
Next time please ask your question in the support thread of that hack.
PS Are you 100% sure that this is a good move?