Planar failing

Hi everyone,

Im working on creating a surface truss that's opennings' respond to the direction of each individual surface.  I have almost finished it, but when the opennings on a surface close completely the planar (which is the result of two two curves, one offset from the other) fails and dissappears.  How can i stop this from happening and just allow the planar to be closed? Can anybody help?!!!  I've attached the rhino file and grasshopper file.

Cheers guys

Jesse