Hi Paul,
I used Nebulosity for stacking for years. I still use it for data capture.
Neb works pretty well but pre-process sub loading and then aligning every sub by clicking on two seperate stars is a pain.
Honestly, go get yourself a 30 day trial of
Astropixel processor, it's soooooo much better, more accurate and user friendly. Then use PS for final adjustments.