Flexhopper, Boucing effect

Hi all

I am trying to make a particle bounce off a mesh.
I am looking desperately in the parameters I cannot find

I thought otherwise to create a soft body, and relaxations between the particles, but it seems very complicated to me

the goal is to simulate a rock fall on a mountain, taking into account the acceleration speeds when the rock falls into a vacuum, the friction coefficient, rock / mountain and possible rebounds depending on the angle of the slope

flexhopper seems more precise to me with physical values ‚Äč‚Äčeasier to define than on kangaroo

Any ideas ?