A few more notes:
In both graphs for T-Max 400, I waited 23 hours between exposure and development. Films have different latent image keeping (LIK) characteristics, and the delay was to simulate real-life usage. I suppose it's conceivable that the two or more emulsions in T-Max 400 could have different LIK decay-rates, so the curve could change based on exposure-to-development delay.
This boomerang is a form of upsweep. In the thread on "Kodak Tri-X- D76 vs HC110 Dilution B (upswept curve look?)", Bill Burk says he believes that upsweep helps portraiture by improving tone-separation in faces. I didn't think of that. I was thinking more of what upsweep would do to sky and clouds.
jp498 said "My highlights are awesome". There are a number of possibilities, one of which is that I goofed. Or you might be using a different batch of TMY2. Or maybe TMY2 with pyrocat or PMK produces a straighter curve. Do you have a Stouffer step-wedge? It would be interesting to get the curve.
Anyway, I exposed a new roll last night, and I'll let it age (LIK) and decide what to do with it once Michael R's results are in.
Michael: If you post or PM your densities to me, I can plot them using my gnuplot script.