custom post type with post_id in permalink structure

There was a closed thread about this same topic by Ne0Que. I wanted to add my word to it.

All the solutions presented here were giving a Page Not found error. But this code worked for me. The extra things I did
– swapped the cpt_id and postname
– added one mroe add_rewrite_tag for custompostname

Remember to:
– replace custompostname, customposts with yours
– flush rewriterules by visiting the permalinks page once.
–
Here is the code I put in functions.php

add_action('init', 'customposts_rewrite');
function customposts_rewrite() {
  global $wp_rewrite;
  $wp_rewrite->add_rewrite_tag('%cpt_id%', '([^/]+)', "cpt_id=");
  $wp_rewrite->add_rewrite_tag('%custompostname%', '([^/]+)', "custompostname=");
  $wp_rewrite->add_permastruct('customposts', '/customposts/%custompostname%/%cpt_id%/', false);
}

add_filter('post_type_link', 'customposts_permalink', 1, 3);
function customposts_permalink($post_link, $id=0, $leavename, $sample) {
  global $wp_rewrite;
  $post = &get_post($id);
  if ( is_wp_error( $post ) )
    return $post;
  $post_link = $wp_rewrite->get_extra_permastruct('customposts');
  $post_link = str_replace("%cpt_id%", $post->ID, $post_link);
  $post_link = str_replace("%custompostname%", $post->post_name, $post_link);
  $post_link = home_url(user_trailingslashit($post_link));
  return $post_link;
}

Hope this helps others.
Am able to get this structure in the URL and all these work:
domain.com/customposttype/custompostname/cpt_id/
domain.com/blog/postname/

Shiva