Ian, interesting formula. Clearly intended to be a solvent developer and would not tan/stain. Regarding superaditivity, I would have thought at pH 7.6 and with that ratio of Metol to Pyro, the Pyro would be doing nearly nothing - perhaps a slight regenerative effect on the Metol, but I wonder if you could simply do a "Haist-76" adjustment (ie eliminate the Pyro and slightly increase the Metol or Borax - or perhaps no adjustment at all). It would be interesting to compare that to this version.