Issues With Making Bone and Geometry Move Between Beginning and End of Bone Chain

I am fairly new to working with rigs in Unreal so it might be that I am missing a very obvious or simple mistake. I am trying to replicate the Mechanics of a Rig I built in Blender but I have not yet managed to achieve that in Unreal 2.25.

For quite a while now I have been trying to combine the motion of my spine bones from Motion Capture Data to a single bone, in order to move the upper body as one big Part. I have had trouble finding a good documentation on the nodes so it was mostly trial and error. I have tried various ways in order to achieve that, but currently I am trying to accomplish this in an Animation BluePrint. The Geometry should be attached to the Backbone, so this is not the issue (as you can see in the Image what it should look like).

My first setup consists of an animation in order to move one of the Back Bones forward to see the results. Connected to that is a Constraint to the child of the BackBone. The Backbone moves along and is in the right position, but the Geometry of the Torso is not moved (see Image).



What it should look like (only works when I set a Transform Bone before the Constraint and enter a value there to a TPose):


I also have a second Setup using a FABRIK, but the Bone is just moving relative to the initial Pose and when this is not a T-Pose it is obviously messed up:

I would very much appreciate any help towards solving my issues!