This 3nm Sii filter is a significant improvement over my previous 7nm filter. Some have complained of uneven flats but keep in mind that cmos sensors have the problem, not the filter, and it all gets eliminated with flats. You can find lengthy forum discussions on this issue. My imaging has greatly improved with this filter and no more halos!
I have done some flat processing and getting really strange results, so not quite sure what is going on. Haven’t had time to follow-up with Chroma or OPT yet.