I wrote "> 700 km". I did that deliberately, and was not asserting that 700 km was enough.

Fair enough but why not just say the much larger other size they specifically mentioned. It's not about it being bigger than 700km but about it being enormously bigger (bearing in mind how volume expands cubed) to a specific size they also name.

Anyhow, sparked me into really thinking about all this again and the link you added was wonderful for that.