Hi, icracer. I do not have the ability to analyze and create curves. I am reporting on both visual examination of the negs on a lightbox, and on prints made identically from representative negs. See more below. i realize that this may seem to leave lots of wiggle room for error to someone used to that level of precision. If I should be proven wrong about this anomaly, so be it; I have no ego investment in this; I'm just following a surprising effect and trying to understand its cause for practical field use.

Hi, Doremus, and thanks as always for your thoughtful and experienced insights.

I am beginning the suspect the same with regard to an emulsion and/or other-layer difference between the formats. I will process a 120 roll (all frames of a controlled subject, identically exposed at EI 400; half the roll processed with the SLIMT and then added to the other half, the two developed together in the same tank with N development. We'll see what happens.

As I have indicated, the low-value boost came as quite a surprise, and if I had not been able to replicate it, with care against variables at each step, I would naturally have dismissed it. I assumed I had made an error with the 35mm after seeing no effect in the 4x5; I tested both again and got the same results as before. I have no idea why this approximately 1/2-stop or so density increase is occurring at the low-end-- as you say, it appears to make no sense, since the higher values are being slightly depressed. It would be interesting for someone else to perform the same test. (And haven't we heard enough claims over the decades about miraculous speed increases?)
As you know, Kachel notes that negative films tend to require the KBr solution to prevent fog, which I am using. I don't see fog, looking at the film or printing, though this is something I can trying printing for, i.e., making prints that place clear film around Zone V or VI to compare them.

I'm not sure how this will all pan out. I can only tell you that I am seeing the same result repeatedly in 35, which I first ascribed to N+1 with SLIMT compared with N without, shooting the same sort of test. And, there is an apparent grain increase evident in the small format enlargements, as usual with SLIMT treatment.