Oh I would not have guessed the concerns were about the tanning/stain? I recall reading (I think on a thread here, I'll link to it if I can find it) that PMK was suspect as to causing lift-off. Simply removing the tanning/stain wouldn't really change that behavior would it? Curious then, what would be the negatives of having the stain? Does it somehow make the emulsion more brittle if left? I find XT-3 is a pretty good developer for CHS ii so I'm not at a big loss to stick with that though since it's the main medium speed film I tend to shoot in 4x5, it would otherwise be a convenient choice to test Pyro-based developers (510 and Pyrocat-HD in particular, though I'm having trouble getting a good direct comparison of the two).
Glad it's working for you Andrew! Does the vinegar/citric-acid have any impact on the stain? I recall reading that using at least a conventional stop tends to reduce the staining affect?