I don't know, I didn't really double-check the math.

The next numbers of seconds in third-stops according to an old Master light meter, 40 - 50 - 64 - 80 - 100

Reciprocity failure is a factor to keep in mind.

I also believe the idea that you get consistent steps using f/stop printing breaks down a little when you change paper grades.

Because 1/3 stop "change" at Grade 2 is a gentle difference... While it's a rather dramatic difference at Grade 4.

Still I'd prefer f/stop differences than 5 - 10 - 15 - 20 - 25

p.s. I made the 11x14 print last night using Looten's 5 - 10 - 20 - 40 - 80, and it sort of caught me off guard. The vintage neg was kind of thin compared to my usual. I had to use f/22 to make that test strip.