Hello Glen
I used this video to help me learn to stack LRGB
https://www.youtube.com/watch?v=XUmbneJTg3Q
In DSS, register and stack your various channels (LRGB Ha whatever) then once you have done that do another register with your already stacked channels BUT make sure you tick "Register already registered pictures" in settings AND in the stacking parameters settings/Intermediate Files tab tick "Create a Registered file for each light frame". Also set one of your lights as the reference frame.
That will create some .reg (red.reg/Green.reg etc)files and they are the ones to then combine in PS.
That's what I do anyway
Hope it helps
Jeremy