Please see my swim cycle animation posted to p.b.a  on 7/21/02.
Note the rotation of the wrists.

My forearms are transformed via:
#declare rforearmtrans=transform{Oritransform(rwristpt-relbowpt,-y) rotate
<0,rwristang.y,0> Oritransform(-y,rtempwristpt-rtempelbowpt) translate
rtempelbowpt}

#declare lforearmtrans=transform{Oritransform(lwristpt-lelbowpt,-y) rotate
<0,lwristang.y,0> Oritransform(-y,ltempwristpt-ltempelbowpt) translate
ltempelbowpt}

For weeks I've tried to figure out what the bug is. But I'm wondering if
this rotation is "built-in" to the orientation.

The wristpt and elbowpt are constants based on measurements I made on a
skeleton.
The wristang is a constant vector (but i get the same results even when I
comment this out).
The tempelbowpt is calculated using FindKnee of Rune and/or JvS and an elbow
orientation vector that is constant.
The tempwristpt is a user-defined function of the clock.
The Oritransform is by JvS.

In other words, I:
i)  rotate from a position based on a skeleton (drawing in 3 dimensions) to
downward,
ii) rotate the wrists about the y axis,
iii) then reorient to a new position based on the FindKnee's new elbow point
and user-defined position for the wrist
iv) translate to new elbow point.

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