Heroku Applications on AWS VPC

I have a small Rails application that I intend to deploy through Heroku (just like other clients), however this is not intended for a publicly available application and they need to deploy it in their VPC VPC as if it is available on the internal network.

Is this something that is possible? I know Heroku is built on top of EC2 but wasn't sure how flexible it was and couldn't find anything documented.

If it weren't possible, someone might suggest an experience of the built-in RMI AMIs that I could use to replicate some of them for easy Heroku deployment without worrying too much about configuring and managing my own infrastructure for the application.