Thx for the reply 
But the disappearing bits can't be caused by the modeldb file i think. I use the same lod, for any distance :
Code:
55 unit_models/_Units/EN_Peasant_Padded/immortal_lod1.mesh 121
55 unit_models/_Units/EN_Peasant_Padded/immortal_lod1.mesh 900
55 unit_models/_Units/EN_Peasant_Padded/immortal_lod1.mesh 2500
55 unit_models/_Units/EN_Peasant_Padded/immortal_lod1.mesh 6400
And i'll check Alletun's Tome of Knowledge 
I think the problem for those disappearing stuff is because i converted RTW file with GOAT, not using GOM's skeleton, and then convert it using GOM's converter .