Mecanim - Body Mask specific bones ( Body Mask for the spine not the hips )

Short version :
I want to create a Layer in my Mecanim control that adds animation only to the spine, and let the hips be controlled by the Base Layer, is this possible? Using a Body Mask, if I set this layer to animate the torso, it animates the hips too, I want to animate only the spine.

Longer Version : What I’m doing is this: the Base Layer have animation for my character walking and idle, The walking animation uses the hips and the legs. I’ve created an additional Layer with animations of my Character looking up and down, these animations uses only the spine, arms and the head, These are the parts I want to animate. If I use a body mask and set it to animate the torso, it animates both the spine and the hips… I want it to animate only the spine, and let the hips for the Base Layer, how can I achieve this?

You need to add new Layer to the Animator window and make new Avatar Mask. Make only the body and the root green and add this Mask to the new Layer. Set the blending to Override. Now your spine animation will override the animations that are in the Base Layer, whenever you call them.