Vectrosity looks nice, but I was hoping for a solution within Unity or PM (not about the cost really but more just adding another piece of middleware that I would only use like 1% of). I think I came up with a solution using a different scaling method - if that's too expensive then I may look at Vectrosity to optimize...
I ended up doing scaling of a game object - I had done it before but with a different method (described above) that led to really clunky results.
Here I used "Get Position" and "Set Scale" and simply recorded the value of the Y position of the hook every frame and stored it in a variable, and then access that variable to set the scale of my cable every frame.
The results are much smoother than before.
I'm not sure if running these actions every frame (inside a small time interval) is expensive (to the point where it's not a good idea) if this is, let me know - but so far I'm happy with it!
Thanks!