Alright, however I tried now to make the geometry LOD with the same model as the table itself. And I cannot walk through it but I'm able to crawl under it.
But if I'd do it like your way I should make a lot of little cubes so the whole table is covered?
EDIT:
I now tried to place a laptop on top of it, but that won't work (yes, wit disable simulation, but not the way it works with an Arma object). Is this also a LOD?