I am not an ABC pyro user, but I use PMK pyro almost exclusively. Yes, an acid fix will prevent full stain development, but a two-minute bath in an alkaline solution (the used developer works extremely well) after the fix corrects the problem. For what it's worth, I have stopped using alkaline fix after having fogging problems. I use a standard rapid fix without hardener (Ilford Hypam or Universal Fixer or Kodad Rapid Fixer) and fix for three times the clearing time of the film in fresh fixer. The fixer is discarded after the clearing time doubles. I often use weaker dilutions than is normally recommended and use the fixer one-shot, with appropriatlely longer fixing times as determined by a clip test.

The use nof an acid fix enables you to use a conventional stop bath, which, for me, seems to prevent the fogging problems (stripes of higher density on my tray-developed sheet film) that I had using the alkaline fix and water stop. I suspect that the carried-over developer was still active enough to affect the the film, and that the portions immediately exposed to the fix, i.e. the corners or a strip at the side or top resulting from the sheets not being stacked exactly on top of each other, were fixed faster than the covered portions, which then got a bit more development. The developer cannot be active, even if carried over, in an acid environment.

The negatives from the fix have some stain, but appreciably more after the two-minute bath in the used developer.

Of course, you have to find what is best for your working methods, but you should be aware that conventional acid fixers are a possibility.

Hope this helps. ;^D)