As Mark and Gerald said, there are no mysteries. The further you move away from 400ISO with Tri-X, the more you block shadows. Even with XTOL, after testing, all I could get was roughly 320. If you want grain and open shadows you can use TX @100-200, expose for the highlights, and overdevelop with Rodinal. You can then print at hard grades (4-5) to get very interesting prints. Having said that, for scanning, it's better to have well balanced, less contrast negatives, since much can be added later. The problem with grain is that any consumer scanner just doesn't see grain the way an enlarger does.