This is looking far more fabulous than we have any right to expect. Thank you for your continued efforts.

Quote - The tube script will also have the animation options added.

I was going to ask about that. :-)

Quote - I know a proper catenary is supposed to be mathematically elusive, but I think I still have code around which derives some sort of approximation...

As I keep saying in a variety of contexts, an approximation is good enough for the majority of uses. I'd happily do my own catenary approximation by fooling around with the markers if necessary, so even the crudest approximation would be a boon.