I used to own a JP8 as well, and was disappointed to learn that JP8V does not have the capability to separate lower and upper into 2 audio channels. They are mixed internally. What's worse, the detune knob in JP8V changes the pitch of ALL voices equally in relation to each other, regardless of upper or lower, so you cannot simulate voice tolerances for pitch(subtle offsets for the controls between each voice, including VCO2 detune).
Both of these are what made the wide stereo sound of the JP8, in dual and unison mode, possible. I think Arturia did a fantastic job emulating the various modules in a Jupiter 8 voice, but they dropped the ball on dual mode.
If you have a very, very fast computer, you can run 2 instances of JP8V, and use presets to configure something like a DUAL mode configuration. The FX preset drop-down in Reaper is the fastest way I know to set this up. Combine that with a controller that sends Midi CC's to BOTH instances simultaneously, and you're only missing one thing from the real JP8: Voice tolerances.