fix wall/gran contact force handling

A special question to the developer:
let's assume a single ball lies on a plane surface exactly at the corner of 6 triangles.
The expected force contribution for a single triangle would be 1/6*f_pw (m*g=sum(f_triangle)).
Now for comprehensible reasions Liggghts only handles the first contact and than checks for all other triangles if there was an allready handled contact with a coplanar neighbour-triangle. This leads to correct wall-ball behaviour and is OK.

But unfortunately for fix mesh/surface/stress the function "add particle contribution" is only called once.
Now I need a position dependant stress output, but it is accidentally which triangle get the full force.

I attached two screenshots, the 2nd one is the result I expect, but in my innocent try I disabled the continue statement in fix_wall_gran and so my particle gets six-times the wall force which leads to a wrong overlap.

The question is how to fix this ? I thought about a map to store all parti/wall contacts with it's wallforces and devide it for every pair by the number of equal particle ids. But I guess this will be memory and cpu intensive.

Anyone a better idea ?

Thanks,
Christian.