Great result, very smooth and detailed.
Do you know if 20 minute subs are optimal for your setup? I experimented and found 5 minutes to be optimal with my 10" and QSI683 which should be similar to yours I guess. I can squeeze more faint details out by stacking say 10x 5 minute subs than with 5x 10 minute subs, S/N in the final image is simply higher. The more light pollution there is the shorter the optimal exposure will be, so I'd expect 20 minutes to be good for a very dark site but not if you are in the city. Anyway, just a thought