I'm curipus about what you have said about grain and PMK. One of the characteristics which I like about PMK is its ability to give sharp prints with smooth grain. Which developers have you compared PMK to, in order to draw this conclusion? If you are shooting a coarse, high speed film, it is the film which you are seeing, not the PMK. I tend to run slow films (Efke 25 & 100) so I'm not concerned with grain and PMK.
I've found that PMK is subject to uneven staining and development artifacts if agitation and development procedures aren't followed exactly. Tank development in a "yankee" type of tank is very difficult, so I switched to trays and got better results. This shows up in clear bule skies, one of the conditions here in the southwest.
The biggest drawback to the green-yellow stain can come in two places, high values and shadows. Since the color of the stain is affecting density of the film in more dense portions, there can be some masking of highlight values. The high values will be more readily seen by trying a sheet or two of graded paper, but your development times will vary slightly. Since you have tested with a step wedge, it would seem that you have sufficient contrast already, but what about high values? Is there sufficient separation in clouds?
The biggest problem I have had with PMK is in the shadow areas. No matter what I did, shadows were always murky or muddy. They never had any "snap" to them and looked muted, a byproduct of general stain. General stain is a double edged sword, great for masking grain, bad for shadows. There is no way to avoid it with this developer.
I switched to Pyrocat-HD this year and have been very pleased with overall sharpness and better contrast in shadow areas. With minimal agitation, the shadows have very nice contrast and better texture. Sharpness must be seen to appreciate how much better it can be with this developer and process. tim