odf,

The YZX rotation order in Antonia's Thumb1 did surprise me a bit. but the rotation order does seem to vary between figures, P4 figures are XYZ, as is V4. Surprisingly M4 is XZY, as are V3, The Girl and SP3.

In P4 figures, The Girl, V4, V3, SP3 and M4, X is always the twist JP channel. I don't know enough about rigging a human figure to understand the significance of any of this.

Quote - Do you use propagating scale? I've heard that is useful for scaling hands.

That sounds like a good idea, provided that the other factors can be wrestled into submission enough to allow the scaling to propagate to the fingers without distortions when the fingers are bent. That sounds like a big ask, fingers are notorious for not scaling well. Perhaps deleting any smoothScale channels and just relying on propagating scale is the way to go.