Actuated structure

Hi all,

I am working on simulating an actuated structure using springs in Kangaroo. In the attached file, I have projected a triangular grid onto a surface, which determines the distribution of the structural components within a boundary. 

Before I start running the simulation, I make sure the rest lengths of the springs are set to 100% their length. Whilst in previous, smaller-scale, simulations the structure stays still when springs are set to 100% their length, in the attached simulation, the structure immediately begins to move. 

Is there something I'm missing in this simulation which causes the structure to misbehave? Any help would be hugely appreciated. I've already spent three days trying to nut this one out. 

Thanks

Justin