Yes - in this particular case a larger box helps only marginally… get nearly identical (0.02Å difference) results for a 450px and 600px box when switching off real space windowing and dynamic masking (and 450px is a very tight box in this case). It’s useful using a smaller box, as 450px refinements are a lot faster to run.
Was wondering if this was because we still lose signal beyond the edge of the box, we do catch it in the corners.
Skipping masking definitely helps in some cases, and often at least doesn’t make things worse. I would have thought it would make NU-refinement slower, but it doesn’t seem to.