Your comment about the look of your Pyrocat negatives, i.e. that you cannot "identify anything unusual on the negative in relation to "stain" as discussed in many threads here and elsewhere" is typical of the reaction of many persons using Pyrocat-HD for the first time. This is due to the fact that the stain produced by Pyrocat-HD is typically brown, or even brownish-black. Photographers who have previously used developers like PMK and Rollo Pyro nearly always underestimate the intensity of the Pyrocat-HD stain because by comparison with the green or greenish/yellow stain of these developers the brown Pyrocat-HD stain looks almost neutral in color. This is not the case, however, and in practice it will be found that the brown stain of a Pyrocat-HD negative will have an impact on the effective printing density of the negative that is as great, or even greater, than the green and greenish/yellow stain of other Pyro developers.
The impact of stain is a very complicated issue and one that, from my perspective, only a handful of people really understand. I am completing at this point a rather long article on Pyrocat-HD that will go up on Ed Buffaloe's UnblinkingEye. com site soon, hopefully within the next few days. In this article I address the question of stain and its impact on varius printing processes. Look out for it as I think you will find some of my opinions on this matter interesting and useful.