uneven/cut out shell structure for Kangaroo simmulation

Hi Daniel and Everyone in this group

I'm working on a definition for a shell structure 

The first part works well where the shell is an even surface

But now I need a more complicated one and the definition seems not to work with this shape

I think It's because of the whole "cut out" side is fixed (anchored) on the starting position and during the simulation it collapses 

So now I'm not sure how can I have it fixed (anchored) only at the part which is "touching" the ground and have the cut out pieces loose ???

(eventually I need to manipulate this surface with the repelling curve in the second part of the definition)

Any help would be much appreciated

Agnieszka