I ended up getting a ton of data on this over most of April as I chased equipment issues: camera and issues with focus. I ended up ditching all my luminance and got a sharper result making up a synthetic luminance from the RGB.The problem finally traced to my flattener which provided a quite flat field but lousy offsets between R and B which made luminance focus worse than focusing individually between each RGB filter. And finally after a year of pain with the new SX-46 (5 different main camera boards) I feel confident that the issues are totally resolved. Over the last year I had project after project never complete due to these issues. This time I was just determined to get "something!" So, this was overkill, no doubt, with 10 hours of RGB (5 min subs) and 16 hours of Ha (15 min subs). Overkill or not, this much good data certainly made certain aspects of processing easier.
https://www.astrobin.com/406649/B/
Full size image here:
https://www.astrobin.com/full/406649/0/
Thanks for looking.
Peter