Unless I’m missing something this seems pretty straight forward.
I created a Quad Group that goes into the 7.1.4 Group.
I created a mono audio track that goes into the Quad Group.
I created a stereo audio track that goes into the Quad Group.
I created an object in the renderer dialog and chose the Quad Group as a source.
(By default this took all four channels and spanned them across four available objects.)
I then just increased elevation to maximum on the Quad Group’s panner. Now those four channels hit the top channels only.
I can now pan the audio tracks as expected. The mono can pan into the Quad group to any individual channel (and thus top speaker) or a combination of them, and the stereo track is easy to keep ‘locked’ in stereo by simply using the knob for front / rear to move the sound between the front pair and the rear pair.
I think that’s what you were looking for, no?