Thought I would post this little gem for the future...
When you export a skeletal mesh from UE and open it in maya, it creates a dummy transform node that contains the rig and the mesh.
Not only is the dummy node named wrong(duplicate name), but you dont want it if you intend to export back this back into ue, as it will break the existing skeleton due to the extra node.
The issue for me was there is no easy way to delete the dummy node in maya - eg by freezing transforms without losing the skinmesh.
(NOTE: I am not a Maya expert in any way - so this confused me for a long time).
To get rid of the dummy node, one workaround is is duplicate the rig and mesh, copy the skin weights over, then delete the original
(For other maya noobs like me)
1. duplicate your rig.
2. freeze the transforms you need to freeze.
3. duplicate the mesh.
4. bind your duplicate mesh to the duplicate rig.
5. select the original mesh and shift+select the duplicate mesh
6. skin > edit smooth skin > copy skin wieghts [option box]
7. in the copy skin weights window choose edit > reset
8. click copy
Hoping this helps someone
