mshchem
Subscriber
For small increments, like 1/12 stop, there isn't much if any difference between a linear progression and a logarithmic progression. The smaller the stop increment the more linear the progression - the basis of differential calculus, really.
A 1/12 stop 5-strip test would start out at a 6% step and finish at a 7% step: 10 seconds, 10.6 seconds, 11.2 seconds, 11.9 seconds, 12.6 seconds. Without an f-Stop timer one might as well set the timer to 0.6 seconds (or 6% of the base exposure (though 5% / 10% are easier on the grey matter)) and be done with it.
A 1/12 of a stop change in print exposure is roughly equivalent to a 1/6 of a zone / stop change in negative exposure (midtones, regular development, #2 paper). Control over exposure can be far more precise when printing than when shooting. Printing can deliver what the Zone System only promises.
Did you (a few years back) sell a f stop overlay for the Gralab timers? That seems like the first time I recall seeing a f stop timer for printing.
My method seems to be make a lot of test prints. I use a Metrolux II timer for my cold light enlargers, this works nice but alas no f stop function, I have a phone app, my problem is I don't always know if a print is X fstops light or dark.