Greg,
Tempting fate here, but I have never had a cable fail. Twice, on different boats, I’ve had the pulley blocks pull out of the adjacent woodwork which in effect gives the same result as a failed cable.
On all three boats, T4, A31/4 and A1 have had s/s cables. None were oversized; none were over tensioned. In fact there was always a bit of play in the system, which is fine as long as it’s not too sloppy.
Agree with Jim – I doubt whether working to and fro whilst on a mooring is an issue.
Don’t have an answer as such, but to my mind, any cable needs to be as flexible as possible. Also check the provenance as I’ve heard anecdotal evidence from more than one source that s/s from China is not up to much.
Mike