Really nice!
I did an LRGB M42 with a 383L a couple of years ago - it works really well with HDR. Each channel I took 9x10 minute, 15x10 second and 27x4 second sets of exposures however I think that could be adjusted a little better by going for a 30-60 second set too. The shorter the subs the more of them you want for better noise reduction.
M42 is one of the hardest targets because of the dynamic range.