I have had other devs use VICODynamics in fishing games, so I’m inclined to say yes. But I have not tested it myself.
The extending is very doable especially with the new SetNewRestLength function which allows for changing the length at runtime. The system is elastic at its core, this is how the solver algorithm works. Hence, being a soft-body system. You could turn up the substep and constraint iteration counts higher to achieve more rigidity, but it will never be perfectly rigid. If you know you’ll have a set number of fishing lines in a level, then you should be able to increase the substep and iteration counts for more rigidity while maintaining desired performance.
Hope that helps.