I found info in my notes from Sandy King for the following, some adjustments will need to be made for TMAX400 but at least it can give you a starting point:
"Times for Tri-X should be very close to those for HP5+, but I have not tested this." SK
HP5+ semi-stand:
Pyrocat-HD of 1+1+150 for semi-stand. That is initial agitation for 1.5 minutes, and then once again for 10 seconds at the 1/2 point of total development time.
HP5+
high contrast scenes, 40 minutes
normal contrast scenes, 50 minutes
low contrast scenes, 65 minutes
Again, I don't use either TMax or Tri-X but the adjustments I have made for Delta and FP4+ (1+1+100/1+1+150) at 64 have come out beautifully. I just personally prefer long dev times. It's a visual thing.
Please post whatever results you end up with so we can all add it to our records.
Don't forget to pre-soak