Luke, Register yourself in FSP like you usually do. Once that's complete, go through the same process again, but when the window where you change your information is displayed, change your class from FSP to TO2. Once all is said and done, check the entry list to confirm that you are registered in both classes. When you register for the next event, be sure that your class is set back to FSP.
Mike, yes, the event is open to everyone. Registration closes at 10am the Saturday before the event. Go ahead an register. If you register and don't show up, nothing happens. However, if you show up and don't register, you don't race. Registration is free.