The material is Polyurethane - I will try to get a specific product link to what we used.
Regarding the hanging system - I published a new picture of the robot and it should show up soon. You can see better there.
Basically, the system is spring-ready and held by a pneumatic system. Once the system is open the springs bring the cylinders up into their final position. Then we can open tell the pneumatic system to push the telescopic cylinders up to their max height.
If more explanation is needed let me know.
A little bit of it is shown in our reveal video:
https://www.youtube.com/watch?v=SjWtlwqr2aM