Neil
No, converting to pseudo-NT was a bad idea, as old devices don't know anything about GMP subfiles. It is the opposite that we need to do, eliminating GMP subfiles.
However, now we can take your pseudo-NT map and convert to non-NT (more precisely, "GMP-free") with process-gmp.
It should work if the original map was non-NT (well, I guess it was, otherwise "convert to quais-NT Format" wouldn't work).