Thanks folks for the feedback, all good, all deserving much consideration.
Here's what I learned. The SD9VE manual ( which I forgot I had & just found after the question) said move the back sight in the direction you want the grouping to move --->. In this case, right. I was surprised that 0.146" was prescribed (0.125" is an eight of an inch!) I was able to bump it over gradually and keep checking. Eventually, I moved it about 0.10".
I now have a grouping around the bullseye, the way I shoot. In fact, I can now group at 10', 21',and 50'. Now, to work on rapid fire accuracy for an action course. I have a lot to learn.
Thanks all for the prompt, good advice.