For a vehicle of this size, the values are okay.
May you change the distance of Lod-Changing:
Lod0: 000 - 200 m
Lod1: 200 - 500 m
Lod2: 500 - 2500 m
With the Model Viewer you can see which distances are suitable to your model.
As far as I know, the symbol will be shown at a distance of 500 m, so then the model can be quite simple, because the symbol covers a lot of the model.