pre-stress in hypar surface

Hi,

For my thesis I'm trying to build a parameterized simple hypar surface template. Using Kangaroo I want to extend this model with a membrane form finding tool to use in the early design phase. 

I came up with this solution (also see attached file). I get a nice result, however I can't find a way to implement 1kN/m pre-stress in the mesh. Do anyone now how to do this?