Could you post a render from a different angle? Something in the middle of a side and a top view.
There is something at the top of its head and body that I can’t see from this angle, but it looks to me that there is some border-effect in your normal map in that area. Damn my english, I don’t know how to say it better… Ok, take your normal map and have a look at the part of it that corresponds to the top of the head and body. Can you see that faint white line that surrounds it? I think it is making your normals on that area to go away from the seam, instead of vertical from the body, and it is enhancing that border. I can see that line on the tail also, but your render does not show that area.
Not sure if anyone has understood anything. 
Besides that, I would like to say this is my favourite entry for this challenge. Good work.