Hi baminga,
Yes, I tried that, and absolutely nothing happened.
I keep going back and recreating the initial mask and try different parameters and so far I do not get a good edge. I will however try using paths and see where the feather appears, because my belief is the problem starts there, and I mentioned that in my initial posting.
In my book a feather should always be centred upon the original edge thereby blending a proportion of each image layer, and this is primary why a single pixel feather seems a constant for creating a believable edge.
I want this program to succeed as I am impressed with how far it has gone to date, and believe the impetus exists to make it.
I cannot get back to it just now due to other activities, but as soon as I can, I will.