bdphil,

Your scenario describes what I have been through myself to a "T"
Remember to keep it simple. at least I have hard time with it.
According to laws of physics If you get the needles set and nothing changes, then neither should the needles. But then there is murphy's law, if it can it will. What i have found ,if i set the needles where everthing is just fine, transition and all,
go ahead and set the high side another1/16 or so richer to
help with the sag during transition. I know if it its set for for a couple times and been flown it shoudln't be the needles.
If these carbs had just a little bit of an accelerator pump ,
boy that would be nice. The other thing I have done and learned from others of the same concern is to mix a little negative curve in your throttle expo to help slow the throw during transition.
And the other thing it helps in ,if you have noticed at a little above 3/4 throttle you don't really have an rpm increase when given the rest of the trhottle is moved up, this will also help in giving a true linear response throughout the whole range.
do several upline full throttle runs listen carefully for any sagging
just make sure you are still not too lean on top end.
You may already know all of this, but this is what kept me from
loosing the rest of my hair.