Kodachromeguy
Subscriber
UPDATE:
https://ia801606.us.archive.org/10/items/img_20170209_214736_1024/Zone VI Newsletters.pdf
If you are interested in the Zone VI Newsletters, I found them on the internet archive:In the 1970s, Fred Picker wrote Zone VI newsletters about the perfect negative. He was deeply into the technicalities of developers, agitation, densities, etc. You can read his newsletters if you are interested in some procedures for calibrating your negatives. He was addressing sheet film, but you can apply it to roll film as long as you recognize that your frames can't get individual development time.
https://ia801606.us.archive.org/10/items/img_20170209_214736_1024/Zone VI Newsletters.pdf