One other point that seems to be forgotten was that
originally there was a single SF crew on each squadron
Xercules, I dont remember having designated SF crews when I was on 24 in 1968. On the larger stream drops a 'more experienced' crew was generally given the lead. I seem to remember a variety of names being given to this role aka 'Master Bomber' although I cant remember the precise terminology!
We all had pretty minimal hours on the Herc which was reflected in our Categories - No B Cats around then and very few C either. The requirement to have a C Cat to carry pax was waived as otherwise nobody would have gone anywhere.