. . . next up, Rodinal 1:100, 18c, 1 hour, constant agitation 1st minute, 10 seconds agitation at 30 minutes.
What I find apparent here, is that there's very little difference in contrast with the 1:25 standard and also very little difference (if any) in terms of grain size, clustering or shape. Maybe with the weaker dilution but increased time, the results are the same. Two ways to skin a cat, if you'll pardon the expression . . .