Hi, I'm new here.
I know it's not really zone system, but this is what I did for my latest roll of TMAX400:
meter something that is dark but where I still want texture (no spot meter, so the are has to be large enough to cover the central zone of the frame), decrease exposure two stops from there (If it said f1.8 1/4 then expose as 1/15). Recompose, shoot the picture.
Now I mixed my first ever batch of Xtol. I estimate that most of the images that I shot will be lighter than "usual" (overexpose to save shadow detail) so I read that I need to reduce the standard development time by 10-20%. So if TMAX400 in Xtol stock is 6 minutes, I will develop for a little more than 5 minutes.
Does that sound about right? Any other improvements to my method?
P.S.: I usually shoot with my Nikon F3 in it's aperture priority mode just as it wants, and develop in Ultrafin Tetenal. So this kind of different approach is new to me.