It is very much a case of what works for you. "Standard" agitation is what you are doing, but some folks, myself included, use way less. It is kinder to the highlights, especially when combined with higher dilution. I have limited experience with T-max developer, but with the HC-110 that I normally use, I find that agitation is the third variable. (Time/temp/agitation). I also rely on a higher dilution to get me the look I want. I use HC-110 @ 1:63 dilution and, after an initial 5 inversions, only agitate every 4 minutes during development, with 2 gentle inversions. I find the grain is crisp and kept at a pleasant level, and sharpness is improved, with highlights in the right range. Overall, development time will need extending with this technique, but a few tests will sort that. What's the worst that can happen ? A negative with less contrast that can be expanded in pp or printing? That's a good fault to have, and you can extend development, or add back some agitation until you achieve the desired look. Remember, expose for the shadows, develop for the mid tones, and agitate for the highlights.