Thanks Michael
Please notice this strange shape (simple way to draw cobra : ) )
In the area were rails are closer the height jump high up. Maintain Height option does not help. Rhino does not do this. Can you fix it in the next version? Or do you have any suggestion how to use better Maintain Height option. I know I can draw a curve defining the height and use it as scaling rail but instead I would think Maintain Height option should have helped but it does not.

Thanks
Olga