Kangaroo - Unary force, shifting affected points with list item

I am trying to create gravity and force simulation on 6 armed cross-like pipe structure. The idea is that by appyling the force to different arms end points. (One arm at the time) The pipe structure would move. Please see slides 1 and 2.

Slide%202 I am shifting between different sets of arm points by list item connected to Unary force. But it seems that when running the script, no matter to which set of arm points I switch to, it is always dragging the first set of arm points.

I am attaching the rhino file and GH too, because it is rather comlicated to explain. Cross Pipe Foce Simulation.gh (23.2 KB) Cross Pipe Force Simulation.3dm (27.5 KB)

Has anybody idea what did I wrong? Thanks you in advance!