You need to double the cable - as my earlier post says, the Rope, Towing Mk IV was made up from two 30ft lengths of 7/8th in (22mm) cable, each length being doubled up, bound around a single eye at each end and spliced together and bound in the centre, around another eye. You can see this centre arrangement in the second photo of Celerity, just above the 52.
As for rust, if a towing rope in operational service ever showed the slightest evidence of corrosion, it would be declared BLR (Beyond Local Repair). It is such a critical piece of equipment that it is maintained scrupulously, because of the risk if it failing under load. In practice, tow ropes were exposed to oil and dust but not rust.
I like to degrease, etch prime, airbrush a steel colour or two and then apply pigments and fixer to taste. It might seem like madness to paint steel cable a steel colour but by doing so, you can get the right patina and, by rubbing the paint off in places, get the effect of use.
This gives you a flavour of the colour of an operational tow rope in use:
Stephen
