Pass the dem through a HullReplacer. Then use the hull to clip the lines

Thank you hkingsbury for suggestion.

I tried to use HullReplacer transformer. It worked on thin surface only (no DEM). This is fine but, as you can see in picture, it seem drawing lines from index 0 point of DEM boundaries to each point of the area itself. I tryed every settings of HullReplacer transformer. Do you have an idea this behavior why? How can I to drape exactly DEM profile? If you want to try, you can use attacched zip file with readers.

Thank you

Corrado