Thanks a lot for the tip! I’ve already looked into doing it that way indeed, but it seems that this uses a ‘screen space’ sort of projection, right?
This way makes it hard/impossible to position objects in the 3d space and match the panorama background… That’s my mail goal here, making a bit more ‘animated/interactive’ panoramic 360’s 
The cool thing about the StereoStaticMesh in my opinion is that it is ‘object space’, so that the coordinates and the position of the sphere(s) around the player are physical,
and can place object inside the spheres and aligning things are easily.
That’s why I was wondering if and how it is possible to export to the GearVR, as this technique works great in the Vive (objects in ‘real’ 3d + stereo background)…
Hopefully it will be fixed/adapted to work on the GearVR? But I guess that a very small part of the UE userbase…