Terrain occluding distance constants

Hey guys, we're hoping to do some tweaking of the distances at which the terrain will occlude billboards/primitives. I notice now you have to be within a certain distance of a mountain for it to obscure features behind it. It wasn't immediately clear to me how/where that was done.

Is there a way we can tweak this behavior for our varying needs? I'm aware of the billboard burying problem and the eye offset solution (which obviously only works within limits), but I'm hoping to achieve a little bit different balance at least as an option for our users.

-- David