Problems with LOD

[Easyglider]

Hello, my first steps with AC3D and Xplane are done. I have made a tower. Unfortunately I can't manage to define different LOD. I defined a group auf Obj. and fixed a near-LOD (0.001) an far-LOD (1.000). After this last step and exporting to XP8 I can't see the Tower anymore. Just the light on top of the tower is still shining. Where is the mistake?

[Easyglider]

I'm still searching a solution for my little problem. To make an object faster in the distance it makes sence to define different level of details. I can't manage it. Is it only possible to define only one group for one detail level? I thought to define a group for a distance from 0 to 1000 meters and one group from 0 to 10000 meters. Is this possible? Or should I define one Group LOD 0 -1000 meter an another group LOD 1001 - 10000 meters?
Who can help me?