Splack 10 beta with serial console

I\'m trying to install the beta on an Ultra 1, not having a sun keyboard to hand, I\'m using a vt320 on the console port.
The kernel boots fine, and takes me to the login screen, but on trying to log in as root I get the messages Bummer, can\'t open /dev/tty2 and tty3, as would be expected given that I only have the one real terminal, these just keep on repeating forever.
In splack 8 there was an option to boot with a serial console, but this seems to be missing in 10. Is there a workaround, or is the only option to install splack 8 and upgrade?