I stumbled on this conversation, but wanted to thank you. In a moment of not-quite-panic, I wondered if describing a footrope, 'no bigger than his thumb' (a fourteen year-old boy off Cape Horn in 1851, aboard Flying Cloud, dead night, sleet) was an accurate representation of his perch.
From these comments I don't think I'm too far off, at least in the realm close, so as not to be completely making it up.
Though the footrope size came from somewhere; I just can't recall the source. So thank you.