Hey Cheng!
Check out the 4748 samurai, he cannot raise his arms either! I think that, to allow movement for the arms it would better to have the shoulder pads clipped upon the arms, not the chest.
I don't like this samurai's helmet, either. They could have use a mask with a grin and a fake moustache with another helmet. More like how I imagined a japanese armor, anyway.
I'll try to find a pic.
Cheers,
Arnaud