Clip terrain from 2D shape

Has anyone found a way to create a clipped terrain from a 2D element that does not create triangles outside the closed shape?

If there are curves or irregular vertices that come back inside the overall shape limits these outside triangles are formed.  Tried max triangle length, slivers, edit surface.  The best way we have found is to create a profile of the shape with the active surface and set the profile active to create a 3D element, then add the 3D element to the clipped terrain as a boundary feature.  Seems like the clipped terrain from 2D element would/could make the boundary feature, but it does not.   It would be nice to have the option on the create clipped terrain dialog to "add element as a boundary".  

Any thoughts?