Hello, folks!

I'm trying to make a simple animation (well, simple in my eyes, anyway).  I want a character to be holding a cup, then bring it to his mouth and have the cup and hand attach to the head for a short bit to simulate drinking from the cup, then returning the cup to the original position.  My idea was the following:

Parent the cup to the hand (in this case, the right hand).  Animate the cup being lifted to the mouth, using forward kinematics on the hand.  At the frame where the cup contacts the mouth, add a constraint, and flip over to IK.  This does have the effect I want to use (where the cup is lifted to the mouth and then "stuck" to the mouth for the duration of the drinking part so I can move the head and have the hand and cup move with it), but the problem becomes transitioning between 0 constraint and 1 constraint.

At the "1" value, the wrist of the character breaks and the joint looks crushed.  I have tried rotating the constraint grouping but I can't get the joint "uncrushed".  And, if I transition between 0 and 1 values, the hand rotates incorrectly.

I know I'm doing SOMETHING wrong here but I can't imagine what it is.  If anyone has some pointers as to how to do this animation better, I'd be greatly appreciative!  The idea I want is the character to be holding the cup on a table, then lifting the cup to his mouth, drinking while his head is in motion, then returning the cup to the table.

Thanks in advance!