I successfully used the shortcode's logic on a CPT post in v3.4.2 and in a CPT page template. However, this plugin's metabox doesn't show up on the "edit post" wp-admin page for Custom Post Types.
Please update the plugin to show up on CPT post editor screens.
Please keep updated/optimized for current WP versions.
I appreciate your efforts. Once done, please specify if you'd like a donation to help with your time. If you want to contact me privately, my email is tko at tourkick dot com