Thanks for your help so far musocity,
I'm a slow learner when it comes to scripts.
I had another crack at it today.
I started in BIAB. I tried to remove all but the stems & drum mix from the project but that doesn't seem to be easy.
I muted everything but the stems & drum mix.
I froze the drum mix
I saved the song with a diff name
I opened Reaper,
I removed the PG VST
I reinstated the PG VST
I opened the new song file
I ran the ACTION scripts one at a time and all three came up with error messages.
Two had, essentially, the same message after selecting the SGU file
The third didn't get that far and threw up its message ASAP.
You see, I'm a klutz, this is why I try not to get into this side of things.
Here're the error messages...

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error2.png (43.8 KB, 119 downloads)
next error.png (71.56 KB, 119 downloads)

Cheers
rayc
"What's so funny about peace, love & understanding?" - N.Lowe