Spacebuild map and Occluder

I thought i had found a great way to reduce the lag on spacebuild maps drasticly. Since A lot of players will build ships and other space craft on planets with tons of models, i had this great idea to protect the open space from rendering these by using occluders. The results were quite satisfying, untill i have encountered a problem. It seems like that Occluder only works on a limited range.

Take a look at these screenshots.

This is a schematic of a random planet that is in my map:

The following picture contains a load of models, causing a very noticable FPS decrease. It is taken from within the atmosphere. The FPS is around 12ish:

This picture is taken from barely within the atmosphere, just outside the occluder brush (which is a sphere). The FPS is quite high here, around 60.

Screenshot of “earth” with the “r_visocclusion 1” command enabled. You can clearly see that the Occluder brush is doing his job. The green lines indicate models that are hidden behind the occluder brush.

Screenshot of “earth”, but at a greater distance. It seems like occluder stops working at a greater distance. That issnt really what i had in mind.

So, is anyone having any idea of what is happening here? And is there a way I could possibly solve this?

Thanks in advance!