What I need is a terrain showing fractals at the distance and not near the camera.

Left part shows a preview of two heightfields (both with the same DEM file) merged with a Distance from Camera shader.
The first hast Fractal Detail on and the second off.
The Distance from camera has correct settings, (I can see the mix zone inside this point of view).
The right side of the image shows the terrain with fractals only.
The center part of the image shows the Distance from Camera Shader settings:
Mix Controls > Mix to A: 0.5
Choose by Altitude: All
Merge Mode > Colour Merge Mode > Mix(Normal)
Merge Mode > Displace Merge Mode > Mix(Normal)
What would be the right parameters to the merge shaders, or the right way to mix the heighfields?
Thanks
Fernando