Digital BW, The Print

Sorry to be taking up so much bandwidth on the group while
converting my 2200 from UltraChomes to UltraTones. I'm almost
there, but I have a question about getting that last few percent
of precision out of my setup before I start seriously burning through
ink and paper. To be clear, this QTR on Linux, with a Epson 2200.

Background: I've installed the UltraTone carts, cleaned & checked 
the nozzles until they are firing perfectly. I have the toner-curve.raw 
file with the correct bit order for Linux. I've installed Carl's 2200 
UT curves, and relinearized them, but did not do the calibration 
procedure from scratch, only entered the new linearization data.

Problem: The output is wonderful, and ALMOST perfect. What prevents 
it from being perfect is that when I print 21step.tif I see a tiny 
discontinuity in the gray ramp, located at a slightly different spot 
for each curve (cool, warm, sepia, neutral), somewhere between 50% 
and 60%. On neutral it is barely visible; on warm, I can spot it with
a quick scan.

A while back I modified the 2200 dot size transition point in my QTR code 
to be 0.45 when I saw a similar, but far more pronounced, problem using 
the Epson UltraChomes. The change made the resulting UltraChrome gray ramp 
absolutely 100% perfectly smooth, without any discontinuity. I'd like 
to get to the same place with UltraTones, since I know it is possible.

Questions:

- Should I be recalibrating from scratch instead of just relinearizing? 
  I would think that wouldn't be necessary, otherwise how can we share
  curves? I don't think I recalibrated with Carl's UC curves.

- Might the optimal dot size transition point vary between ink sets on 
  the same device? I haven't tried changing it yet, but I would be
  happy to do so if that's the problem. Simple enough. 

- Is my expectation wrong, that the ramp should be totally smooth?
  I have no evidence this is image-affecting, though I could posit an
  image in which it might visibly manifest. It would tell me 
  a lot if, for example, other folks who've been through this said, 
  "Yeah, that happens, don't sweat it. Shut up & print." Or the opposite.

Thanks for all advice. I'm soooo close to nirvana....
david