Yep, but have you double checked for availability now? I was able to move my reservation the other day. Well, you can't move it, but first I checked for availability by pretending to book a reservation. You can't actually book it though (because you can only have one). Then when I saw that there was a time I wanted, I went into another window and cancelled my current Palo and rebooked a new Palo in the other window.
But yah, what OKW Lover said, you can also see what's available on board. They hold a certain portions of reservations aside.