Nice result Tony. I think it is a tough game at such high resolution as you have (under 0.6" pp) - it is way past diffraction limit of your aperture and I'm wondering whether it would be worthwhile to experiment with binning 2x2 which would boost the SNR with not much loss of resolution in this case, and some detail could possibly be recovered with drizzle integration.
Halos around brighter stars remind me what I used to have with my ED doublet and 3nm filters - some out of band signal leaks through even the best narrowband filters resulting in halos, albeit in my case these were more pronounced because of using a doublet. I suspect it is predominantly blue signal that is causing halos around brighter stars. This is why I do not think that narrowband works well with achromats, since we can get halos even with triplets.
I noticed that my 12nm Astronomiks were giving me more noticeable halos with my ED doublet as opposed to 3nm Astrodons. It might not be only the bandwidth, but also how well both block out of band signal. I made a quick compassion here:
http://www.iceinspace.com.au/93-770-0-0-1-0.html