Well there seems to be some mysterious forces at work here
Despite all of my efforts I could not get the MT reduced stars in the star mask of my IC5070 image (as sent to Harry and Carlos), to remain reduced in the underlying image, when the mask was removed.
Yesterday I uninstalled PI and re-installed it, but no change.
Tonight, Harry successfully managed to make it all work on my image, and 'posted' a video of it on his website. So I followed Harry's move's one-by-one, and still it wouldn't work for me.
In desperation, I again uninstalled and re-installed PI, tried it yet again, and it all worked 8)
Now, it has often been said that astro image processing is a 'black art', maybe now I'm starting to believe it
Dave