Automatically add menu item to WordPress Menu - wordpress

Question

I found this sweet plugin that will automatically add a menu item to your custom menu for pages. All I need to do is tweak it to work for a hierarchal Custom Post Type. I'm thinking it will be easy for some of you... hopefully :) Thanks in advance.
Here it the code:
class AutoSubmenu {
/**
* Constructor
*/
function __construct() {
add_action( 'publish_page', array( &$this, 'on_publish_page' ) );
}
/**
* When publishing a new child page, add it to the appropriate custom menu.
*/
function on_publish_page( $post_id ) {
// Theme supports custom menus?
if ( ! current_theme_supports( 'menus' ) ) {
return;
}
// Published page has parent?
$post = get_post( $post_id );
if ( ! $post->post_parent ) {
return;
}
// Get menus with auto_add enabled
$auto_add = get_option( 'nav_menu_options' );
if ( empty( $auto_add ) || ! is_array( $auto_add ) || ! isset( $auto_add['auto_add'] ) ) {
return;
}
$auto_add = $auto_add['auto_add'];
if ( empty( $auto_add ) || ! is_array( $auto_add ) ) {
return;
}
// Loop through the menus to find page parent
foreach ( $auto_add as $menu_id ) {
$menu_parent = NULL;
$menu_items = wp_get_nav_menu_items( $menu_id, array( 'post_status' => 'publish,draft') );
if ( ! is_array( $menu_items ) ) {
continue;
}
foreach ( $menu_items as $menu_item ) {
// Item already in menu?
if ( $menu_item->object_id == $post->ID ) {
continue 2;
}
if ( $menu_item->object_id == $post->post_parent ) {
$menu_parent = $menu_item;
}
}
// Add new item
if ( $menu_parent ) {
wp_update_nav_menu_item( $menu_id, 0, array(
'menu-item-object-id' => $post->ID,
'menu-item-object' => $post->post_type,
'menu-item-parent-id' => $menu_parent->ID,
'menu-item-type' => 'post_type', /*array( 'post_type' => 'bio_diversity')*/
'menu-item-status' => 'publish'
) );
}
}
}
}
$auto_submenu = new AutoSubmenu();