Master RunAction accessing PrimaryGeneratorAction


My code works in sequential mode but not in my multithreaded. I have an automated file naming system that gets information from a PrimaryGeneratorAction member variable (which is fixed for the run). This is appended to the filename in the BeginOfRunAction. For example, file could be Sim_Energy_1MeV.root

On the Master thread, there is no PrimaryGeneratorAction (PGA), therefore, the filename is left blank but the local thread file names are correct before the analysis manager merges them into one matching the master. i.e Master: Sim_Energy_.root, threads Sim_Energy_1MeV.root

Is there any way the master thread could access this information from a thread PGA easily or a way for the analysis manager to use the thread filename and ignore the master when merging? I am also using Geant4 10.3.3 and understand functions may not be available for this task in this ageing version.