I think I've got it in the right place, according to Samsung's instructions. It does feel the most comfortable too. Any lower (towards the wrist) and I can't twist and pull my hand back comfortably. Any further higher (away from the wrist) and it just feels wrong. Plus it probably wouldn't stay there as my arm tapers a fair bit towards my elbow.
If I slacken off the wrist band. Then I have to keep inputting my PIN. As it thinks I've taken it off my wrist as I move my arms about a lot when working.