Thanks again for all of the advice on Diafine. Last weekend I shot one roll of Tri-X at a basketball game. The only telephoto lens I have for my Minolta 7000i is a 70-210 f4, so I used that, set mostly at 100mm. I set the meter at 1600 and the shutter at 1/125, although the camera's meter thought that the scene needed 1/60 at 4.5.
I increased the agitation from 5 seconds every minute to 10 seconds every minute.
I printed a contact sheet which looked good to my standards as well as a 5x7 print of one frame. The 5x7, which I printed at a contrast level of 2, had decent contrast and enough shadow detail for what I was trying to do. The grain was no more than what I expect from Tri-X and considerably better than a previous experiment I did with HP5+ rated at 800 in Diafine.
I fully expect that some of my shots will be a bit blurred because I shot them at 1/125, but if I get 10 good shots out of 36 I will pleased with the results. I will definitely try this again while I save my money for a faster lens.