Maybe we need a new title for the thread? Or perhaps a new thread now that we have a few booked? Just a thought. Well, 2 thoughts.
A tip for anyone else who might want to book a single cabin. IME cruise lines will not always sell single cabins, even at the full 2 person price and even if there are spare cabins for sale to couples or groups. It's probably a breach of anti discrimination laws but whatevs, I've never been bothered to complain. But my suggestion if you're wavering would be to book and then think about it, and cancel before the penalty period if necessary, rather than think about it then try and book and find out you can't book a single cabin even at full price.
I've sometimes thought about inventing a fictional second pax and then just saying at the dock that they're a no show, but I'm not quite brave/silly enough to try it in case I get denied boarding.