Hi Walt nice to see/hear from you. Simple answer is yes and because I could ? the main difference between V4 and V 3 of the Jup-8 is the V4 has Arturia's new sound engine.
None of the Arturia V3 patches appear to be available on the V4. The actual structure of the synth is different.
In the Advanced section The Galaxy Modulation is gone has gone, in the V4 you now have two additional LFO's and a Modulation Mixer I suppose it is the same idea but arranged differently. The Keyboard section now has four curves for Velocity, Aftertouch, Mod Wheel and Keyboard Tracking, instead of just the two in V3.
In the effects section you only have three FX with no distinction between Upper and Lower voices FX. V4 does not appear to have upper and Lower voices anymore. It is much more in line with Roland's own Jupiter 8 on their Cloud which has not Upper and Lower voices.
I was also making a tune that used Jupiter related synths so I used all the Jupiter or Juno type ones I had.
Nice to hear from you though hopefully we will hear some of your latest music?