I don't doubt that you have had success with this Andrew, but do note that the Kodak literature (J86:
http://www.kodak.com/global/en/professional/support/techPubs/j86/j86.pdf ) expressly recommends T-Max RS instead of T-Max for replenishment, and also recommends 45ml rather than 70 ml per film.
Did you start out with the Kodak recommendation and then refine it to taste?
I'm also curious - you recommend adding the replenisher before processing, while in my experiments (with HC110) I ad the replenisher before returning the just used developer to its bottle (with any overflow being discarded).
I wonder what effect the two different replenishment procedures (i.e. their timing) might have on the result.