I'm having a similar issue, however after installation, if I let the installer reboot, while the ISO is still attached, the install will boot normally, and continue to do so as many times as I reboot, however, as soon as I shutdown the VM (either shutting down from within the VM, or shutting down in FN UI while at a GRUB menu), it can no longer boot from the Zvol I've assigned it.
Are you seeing similar behavior, foefyre?