Flexible shaft modelling in SimMechanics 2G

Hello, I'm modelling a legged hexapod robot equipped with series elastic transmission from motor to links in SimMechanics 2G. I managed to get a full working model, but I have no clue on how to implement the compliant driveline, that in the real robot is represented by a long torsion shaft connecting joints to motors. There's the possibility to add a joint stiffness by specifying a spring constant value in the internal mechanical parameters, but I'm not satisfied with that since I don't get the results I'm expecting.

I saw this flexible shaft on SimDriveline, but I have no idea whether it's possible to integrate it in SimMechanics.

Is it the right tool for me or should I look for something else?

Cheers Marcello