How do I determine the normal and shear stiffness for elastic supports? I've been using the SW 2018 tutorial for reference as it is the only one I can find that even mentions elastic supports. The tutorial has you set an elastic support  on the bottom face of the assembly to "(characterize) a thick sheet of rubber" Looking on google it seems there are multiple answers for how to find axial and shear stiffness, but none of them correspond to the 1000 lbs/in/in^2 from the tutorial so I am assuming I am looking at the wrong one. 

I've tried looking at different types of rubber to rule out me looking at a rubber that is different from the SW tutorial.