restricting access to questions and answers to just members

I'm using cart66 so people can purchase digital downloads and sign up as a member on my website. I would like to offer the Q&A to just those members who purchase my product. I can't see a way to do this though because the Q&A plugin uses custom post types, and so there's no physical page where I can wrap the plugin around with a shortcode. The cart66 plugin gives me the option to use a member level that I can define such as "basic".

[show_to level="basic"]content[/show_to]