I never find the optimal time for most of these "mixes" to really be a minute appart...
Again... I think some of the folks chiming in have never DONE it. I have and I posted my impression of REAL results.
APUG makes me nuts with folks guessing about stuff that they have no experiance with.
That massive dev chart is like the Wikipedia of processing. I have doubts about real testing and situations. For ME I have always found HP5 to be an ISO 250 film if developed by the ilford chart... and that's from Ilford, not some Wiki developemt chart.