If you've ever tried bleaching back the stain image you get from pyro development, you'll understand why an acidic stop bath is nothing to worry about. The dyes that make up the stain are extremely persistent. They easily survive an acid stop bath and acidic fixer.
I have no experience of staining developers but I know of at least one video presenter who otherwise seems to be reliable on processing who advises against a stop bath. I feel but cannot state for certain that I have seen others suggesting the avoidance of an acid stop bath as well
Is this yet another myth that gets quoted as if it was based on real evidence but in fact anyone doing a simple test of using acid stop and then not using acid stop would find that there is no difference to the stain?
Can I ask if you have done this test yourself with a 510 pyro developer and is it possible to show us the results?
I appreciate that you mention trying to bleach back but is this the same thing and are you referring to bleaching back after fixing and washing? Again I have no idea about whether there is any difference in terms of outcome between dev; acid stop; fix and wash and dev; water stop; fix; wash and bleach back
Hence my need to ask questions
Thanks
pentaxuser