How do you boot from the internal optical drive in Heads?

How do you boot from the internal optical drive in Heads?

When Heads starts, it doesn’t mount the optical disc (and hence doesn’t see its OS as a boot option). I don’t seem to be able to find any option where I can change the boot disk to any type of media except USB drives.

/dev/sr0 shows up and can be mounted from the recovery shell. However, the command to start a kernel is fairly complicated (Heads Recovery Shell | Heads - Wiki) and depends on finding the right boot directory on the disc.

Is there a way to get back into the Heads boot options after first going to the recovery shell? That would be the easiest probably if I could mount it first and then hopefully it would show up.