Is there a way to rectify root movement mask

I'm trying to mask an attack animation out of a mixamo rig, with humanoid type.

But this rig uses root animation in the attack animation, meaning it rotates the whole body to achieve the upper body movement.

How can I mask the upper body movement when the upper body animation controls the whole body animation?

I realize this is a mixamo question, and I've asked the question there but the response time seems long,

thanks for any advice,

 

The upper body should not control the whole body animation. The whole body animation should be controlled by the root bone which is located at the base of the feet.
Documentation excerpt - and Root (which is denoted by the “shadow” under the feet).
http://docs.unity3d.com/Manual/class-AvatarMask.html

Can you not mask only the torso, head and arms for this specific animation, while leaving the root and legs out of the mask, using the base animation?

Alternately use Transform mask
Documentation excerpt
if you want more detailed control over which individual bones are masked off, you can use the Transform method to select or deselect portions of the model’s hierarchy to mask. To do this, you must assign a reference to the avatar whose transform you would like to mask off, then click the “Import Skeleton” button. You will then see the hierarchy of the avatar listed in the inspector. Each bone has a checkbox allowing you to select or deselect parts of the hierarchy to use as your mask.