Trouble with Montage + Layered Blend per Bone

https://forums.unrealengine.com/core/image/gif;base64
​Hi guys!

Please, i need some help. I am trying to allow my Anim Montage (it is a throw animation) to be blended with the my Locomotion State Machine. With this, i can use the throw while running or jumping.

I created the montage and then used a layered blend per bone, as follows.

Right now the Blend Pose animation appears to be blending with the Base Pose anim, which makes the throw weird (different from the montage / original animation).

But i need that the Blend Pose animation (throw) fully override the Base Pose animation (walk or jump) from the “Spine1” bone, to allow the arms to move just how they are moving on the throw animation used in the montage (UpperBody), while the legs moves according to the base pose.
I need the blend pose to be added as original (from the selected bone) to the base pose, allowing the arms and spine bahavior like the original animation used in the montage.

Please, any help would be very appreciated.