Outerra Forest parameter
I have just found the forest parameter in Outerra'a environment rollout. Lowering the min slope and raising the max slope gave me this beautiful view.
My Environment settings
I get, what I feel is the correct amount of trees in Lessay and a Stoumont
The Luch in overwatch at Lessay Airport and as it is Outerra the terrain will have correct elevation. I used the google map option to place the hangar and runway in the exact same spot as real life