I just read this in the Diafine PDF:
"Because Diafine is a true two-bath developer, each film type is developed to a fixed degree of contrast, and changes in the developing times will have no practical effect on the final results."
This is different than Thornton's Two Bath (not a true two bath), where times definitely have an effect on the final results. I'm now wondering how much the agitation recommendations for Diafine relate to Thornton's given the differences.
At this point I'm thinking limited agitation in Bath B (5 seconds every minute and let the shadow development do it's thing (this is basically what I have been doing except I was using 15 seconds initial agitation)). And stick to changes in agitation (and time) using Bath A where you have real control over the highlight density.
Thanks again to everyone for contributing thus far.