Hi Lee,
I think the size of halos may also depend on the optics, in particular with refracting telescopes
For example, my doublet does not focus all light equally; say when I focus for red colour, blue will be quite out of focus and spread out, thus even with 3nm filters with longer exposures and bright stars, signal very slowly builds up around the stars. No filter surpasses 100% of the unwanted signal. For that particular reason, in spite of being pure "narrowbander", in the future I would like to move to a quality triplet.