'Fine grain, good acutance, fine gradation, mild edge effects'. Yes, I believe Perceptol 1+3 will do all that, and that's why I thought it was not an insane idea. I've used it with many films, but never with Delta 3200 or Kodak p3200, so I'm curious how well this combintaion works.
I brought up D76 1+3 as a well known reference point. For me, Perceptol 1+3 gives similar results, yet seems to be slightly sharper looking with slightly finer grain. (I'm referring to the standard D76 formula here, not Kodak's buffered, packaged version). The catch is the longer developing times. However, since metol is the only developing agent in Perceptol, you can process at higher temperatures with much shorter times. I regularly use 27C, 28C in August with this developer without any problems. That is, at least with film from Fuji, Kodak, Agfa or Ilford. I don't know how film from other manufacturers would react to higher temperatures. You can't or shouldn't do this with a MQ type developer; I notice Ryuji Suzuki suggests no higher than 22C for D76 type developers.
Something else interesting: Richard Henry's tests in Controls... show basically identical results for straight and 1+3 dilutions for granularity and acutance (p225ff) for Microdol-X (which can be considered to be a stand-in for Perceptol). However, he used machine processing, with constant agitation. This suggests that you could adjust your agitation scheme to get the best combination of fine grain and adjacency effects. Ie, if your photographs look too sharp, too 'edgy' or if the grain is not fine enough, you could increase agitation.
Another good feature of Perceptol: no hydroquinone to dispose of.
Tom, thanks for the link. I was familiar with Ryuji's earlier versions.
Regarding the change in developer pH with dilution: I found one reference in Henry's Controls..., p35. Essentially very little should be expected; experimentally, he noted a drop of 0.1 from undiluted to 1+3 in Dektol.