Thank you Troy.
It looks like the NII filter works nicely - no halos and no reflections, same as with my other Astrodons.
Got some initial NII data last night and have attached a comparison of OIII, Ha and NII for the Helix. NII needs much more data still so I will wait before I make an attempt at putting it all together.
In the meantime I have been experimenting with Ha master and slowly getting where I would like to get with the Luminance. Since neither OIII nor NII have the outer bows, I will most likely only use Ha for luminance.
Here is a gently processed Ha data with no decon and no noise reduction applied:
https://www.astrobin.com/full/359357/G/
Thank you for looking