Rudi, I couldn't agree more. I feel that I will have to do a fair amount of testing for the residuals, and just keep a score of what goes through my fixer attempts. Ammonium thiosulfate 60% is not cheap, but it works out the same price (or marginally cheaper) as the ready-made standard, acidic product from Ilford, and much cheaper than the specialised fixers from smaller retailers. However, it is not the price that drives me to do this. Having said that, if I had access to TF-5 at a price similar to what our US friends pay, I probably would not be formulating something of my own.
Still, I would be researching, and perhaps testing, with regards to the function of sodium sulfite wash-aid on fixer capacities, and I'd love to know if ammonium thiosulfate in KRST helps, but I guess I am repeating myself. I agree with you how curious it is how little there is to be found on those interesting points, which clearly have an impact—or Ilford and others wouldn't have mentioned it.