jdef, for what is worth I use rapid fixer and have had no problems. If you loose some of the stain you can always put the film back un the spent developer. Or you can put the film in a bath of sodium metaborate. I actually have found that using a second "staining" bath causes too much overall stain. In my process I just do a sodium metaborate pre bath, developer, water stop bath and rapid fixer without the hardener. It works great for me.
I may add that rapid fixer with the hardener is much more acidic and might remove some stain. But without the hardener it works great. So next time you buy rapid fixer just dont add the little bottle with the hardener and you will be fine.