Hi Peter,

the rough contact (also works with frictional) is the contact between both parts of the helmet when it closes around the head (the contacts corresponds to each cross sections, the front part being the target).

I'm running a new simulation on system C witht the contact stiffness updated at eah iteration and I'm now adjusting the pinball radius to avoid the singularities but there is much less penetration.

However the system C was easier to solve than the F so I don't know if these parameters will still work.