Yes, I realised it works that way, also for walls too - even if I set LOD to 25 for a very long SObject, after export I see the whole thing......When it comes to SObjects you have a string of 'small' objects, but the way BTB makes the SObject, it becomes one gmt (object) in the game. SO if you have an SObject that is 5km's long, with a lod of 2000m , you are drawing that entire object when you are miles from where you need to be able to see it.
So, in this case with a lod of 2000, you want your SObject to be no longer than 2000m. But, if you were to drop the lod to 1000, you would want it no longer than 1000m.
Does that make sense? It's not just 1 factor involved in the equation, there are a few that need to be considered
I think the best way to give you a precise answer is to actually see the object you want to use as an SObject. If it is complex, then it might be best allroud to not set it as an SObject and use it as a single individual object. ie; if it is a fence, make the sections in 100m lengths and join them together manually.