OK, don't know how helpful this will be to anyone since it's possible no one else would be dumb enough to swap the wrong choke plate and shaft into their carbs, but the correct choke shaft and plate seems to have done the job. With it set at closed when cold, it opens all the way when fully warmed up. Will let it cool down now, and possibly make slight adjustment but I think it's really close now.
Here's the comparison of the two choke shafts. Correct one is visibly larger.
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