Each installation into P3Dv4, and P3Dv5, installs a separate copy of ACE to the Prepar3D vX\Captain_Sim\ folder (i.e. 767-II\ace folder), and each copy of ACE works independently of the other. They are also listed separately in Windows Start Menu > Captain Sim (see attached image)

So, for example, if you open the ACE for the 767 Captain II for P3Dv5, it will only have an affect on the 767 II installed in P3Dv5.

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