Create a Prefab from imported Assets automatically

Hi folks!

My goal is to reduce manual operations over imported assets. I've just see that it's possible by using AssetPostprocessor.

As first step I want to make a prefab of the imported object just after import and I tried with these few code lines:

 class FBXtoPrefab extends AssetPostprocessor {
     function OnPostprocessModel (g : GameObject) {
     PrefabUtility.CreatePrefab("Assets/Prefabs/Tiles/" + g.name + ".prefab", g);
         AssetDatabase.Refresh();
     }    
 }

It seems to work, the prefab is created and it have all nodes and materials of the imported model but...the mesh filter is empty :(...

Tnx :)