Rec. Sail size is 4.5-7.4. That's optimistic. Realistic sail size: 5.0-7.0? So whatever you can handle with a 5.0. In practice it's probably not the sail that will be overpowering in 5.0 conditions, but the chop. The starship looks a lot better than a magic ride for taking care of the chop, so you can ride he starship a lot longer than a 'magic' ride.