Oh, I've changed things around again multiple times since my original post. Of course ...

Went back to #20s on both axes and set my clutches precisely to the point where the Y-axis would return to dead center every single time when I let go of the grip. Found that was too light all around for my taste. So, for the 1,000,000th time, I undid the velcro, opened her up and this time I simply started messing with the clutches while the stick was connected and VKB config was running. Just so that I could immediately verify the effect my last change had (if any). I also went with tiny steps on the adjustment screws... no more than, say, a 10th of a turn at a time.
I ended up with the #30 spring on the Y-axis, #20 on the X-axis. X-axis is now set to light to medium clutch, but not too soft, since having too much of a difference in "hardness" between X and Y felt very odd to me.
Y-axis is set, maybe, a hair stronger than what is needed to reliably return it to dead center on its own. It'll still return to center on its own ~98% of the time and when it doesn't, the point where it stops is so close to dead center that it doesn't really matter. Also re-checked my deadzones, but I had already put in 4% center dead-zone in IL-2 which I find works perfectly in that game. As much as I hate the disorganized way IL-2 makes you map your keys, I do love their instant stick input verification feature on the axis fine-tuning screen. Makes it pretty easy to tune the axes and to understand what the various settings will do.
I think what I found out re my personal preferences is that (probably just like in a real plane) I have to have X's and Y's feel "harmonized" (as stated above). The worst the stick felt to me was when I had set the Y-axis to #30 spring and very strong clutch while the X-axis was using #20 with clutch set to its weakest (just above the point where its screw would fall out

). That felt totally unnatural to me.
What I also realized (again) is that at some point you should probably stop messing with the settings or you'll be chasing your own tail, getting nowhere. If you find a setting that feels only "ok" or even "good" at first, leave it like that and start flying, flying, flying. Chances are, you'll get used to it pretty quickly.
S.