Allow Administrators to upload any files

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I want to allow members of the "Administrators" group to upload any file, ignoring the list of allowed extensions (i.e. allow me to upload exe files, but don't let anyone else!). I tried editing models/permissions.php with the following code, but it made no difference in the dashboard file manager when uploading a single file:
// before:
function canAddFileType($ext) {
   $ext = strtolower($ext);
   return (in_array($ext, $this->permissions['canAddFileTypes']));
}
// after:
function canAddFileType($ext) {
   $u = new User();
   $g = Group::getByName("Administrators");
   if($u->inGroup($g)) return true;
   $ext = strtolower($ext);
   return (in_array($ext, $this->permissions['canAddFileTypes']));
}

Does anyone have any suggestions?

Vahan