Based on my experiments, vitamin C developers are very good in two rather extreme conditions. (1) high concentration of reductants, low pH, moderate sulfites. This condition is in agreement with what's described in XTOL patent. (2) low concentration, low sulfites, high pH. This is more like Ilfosol-S and original Gainer formula. However, I don't understand the benefit of compromising in the middle by switching to hydroxide + borax or metaborate solution. If smoother midtone gradation and finer grain without losing sharpness is the purpose, I see D-76Ad (1+1 or more dilute) type formula is better suited (With films like HP5+ and TX, it's hard to lose sharpness. The appearance of each visible grain is also still crisp.). Gainer states in his article that one of his aim was to reduce the sulfite use in the formula. If that's the purpose, I think the resulting formula is reasonable, though I prefer some 30g/L left at the working strength (100g/L is too much and unnecessary).(posted 8102 days ago)Also, I see ascorbic acid and metol getting oxidised together even in acidic solutions of high sulfite/bisulfite concentrations. Even if you prepare split solution, I recommend to keep them in gas-tight containers and spend them rather quickly, especially because Gainer-type formula omits a preservative. (One might argue food products employ vitamin C as a preservative, but those products have relatively short shelf life once the container is opened - maybe 1 to 2 weeks at most.)
Just my random observation.