slim: start second X session on tty8

I am using slim login manager and LXDE desktop environment. When I am logged in in LXDE, and switch to text console (ctrl+alt+F1), I can log in as another user in the text console and type: startx -- :1 vt8 which will start another X session on tty8 and automatically log me into LXDE. While that works OK, I am wondering whether there is a better way to do it. Using startx circumvents the login manager completely. There must be some advantage in using login managers, otherwise we would not need them, and I would log in into my regular X session (tty7) using startx. Is it possible to start my login manager (slim) on second graphical console (tty8) automatically, so that I can log in, without having to use startx?