Help I Have Trouble When Adjust Scale of Model

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1.I import an armor-man model with some cloth i want to add obi cloth on it, it seems good when i do like the video said, but when i make the scale of the model smaller, the cloth that i added obi cloth seemed smaller and position was awful. I uploaded the picture and you will know what i excactly said.[attachment=636]    
2.You can see the cloak cannot move with model's head, i'm not sure if it can move with the head by using obi cloth or i should use animation to do this.    
Thank you guys.