Yeah - testing and removing instances on tick via line tracing might not be the best thing performance wise. BTW - the LineTrace node above is not needed at all in that screenshot - you can just calc the distance directly from instance and ship locations. But you dont want to check every ship every frame anyway.
How do you know the HISM isnt culling?
A fun way to verify culling is to use ~FreezeRendering, then use ~ToggleDebugCamera to eject and fly around the map. You can see what isnt being rendered this way.
Be sure to check the culling properties on the hism component. By default they are set to not cull.
As a simple alternative, you could also just partition your map into multiple ism components. These should cull when entirely outside view frustum.
I find this tool very useful for working with instances:
And this video is informative:
