Thanks for the feedback everyone.
Yes the default scene is where I am starting from, but the flattened part needs to extend farther out. Basically I would like the hills\mountains to start where the haze does or a little farther. (works better for my purposes in game engine)
And also at some stage (for other skyboxes) I will want more dramatic mountains so I am guessing if I change the height for distant mountains the terrain under the camera will also change from being flat.
Since I am working with 6 cameras to capture the environment, I figured some way of altering the terrain itself may be easier. Like, tell the terrain shader somehow where the camera is and flatten out for given distance under the camera - but hey total newbie to all this
But will now digest all the suggestions here and see what I can get working.
OldFlak....