Re: Group Administration
You don’t have to hack the core 
the $bp global contains as values the item that have to be displayed,
if you make those values = false
look here:
$bp->bp_options_nav[$parent_id][$slug] = array(
'name' => $name,
'link' => $link . $slug,
'css_id' => $css_id
);that’s what bp_core_add_subnav_item does
you’ve to do that:
if ( !is_site_admin() )
$bp->bp_options_nav = false;
and make it as a function that has to be called back with the add_action function
