I am using a steel tank that will accommodate a single 120 roll (Hewes). All my measurements assume 450mm of chemistry is a "full" tank (which gives me sufficient air in the tank for the chemistry to move around during agitation). In terms of Rodinal dilution, I have been using (roughly) 1:50 - basically, I just measure out 9mm of Rodinal, dump it into my mixing cup, and then fill the cup with water until I have 450mm, letting it cool in an ice bath until it is around 20c/68f.
I am using the spot-meter function of a Sekonic 758DR. In most instances, I will meter for the darkest area of shadow in which I want to retain meaningful detail/texture and then stop down two stops. To date, I have been metering using an EI of 100 and have been bracketing one stop over and under. The shots that have been given a stop more light typically look the best, but in some instances are almost "too" contrasty, which is why I think that instead of going to ISO 50, I am likely to try my next roll at an EI of 64. Again, I am very new to all this so I don't have a cogent explanation for that. Perhaps Rodinal loses speed? Perhaps it is simply my aesthetic that likes a contrastier negative? In any event, because I do not have a darkroom at home, I have to use a community darkroom and have not yet had the opportunity to print any of these negatives so, as I said in my original post, I am taking this all with a grain of salt for the moment...
Hope you are well,