Funny you should bring this up- I was up late last night testing TMAX400 to get my personal film speed. I actually rate TMAX 400 at 50 (!). So, in my darkroom, you'd find you have underexposing a stop!
This is based on some film tests I did to get a zone 1 exposure equal to .1 density over fb+f. I am using HC110 H dilution (twice as dilute as B), in a jobo drum on a Beseler roller.
Seems odd to rate it so low, but I don't care. I know I'll get detailed shadows. I guess I could rate it at 400, and put my shadows on zone III or IV.
If I rate at 400, and put shadows on zone II, there is not much density there on the negative to print...
TMAX 100 I rate at 32, using the above developing routine and zone 1 density target.