This is really strange - if you have Cubase 7.5, can you just check to see if the Stereo Dual Panner is actually available from the drop down list to the right of the panner? Because for me, there are just 2 options, Stereo Combined and Stereo Balance. I agree in the Prefs under VST, there is Stereo Dual Panner (Remote Control Devices only) but how to select it for a channel??
BTW I was having problems even finding the Panner drop down option hotspot - sometimes it was there and sometimes it wasn’t, but I just updated to C7.5.1 and it seems to be there all the time now, but only if you roll the cursor from left to right, the other direction doesn’t show it.
I really hate these hidden hotspots, they make my workflow infinitely worse because I waste time trying to find them.