Mecanim MatchTarget & Generic Rig

Working on a project where we are using mecanim to drive most of our NPC's movement, but want to be able to control the Y position of the character's via a c# script. From the Mecanim tutorial video, using MatchTarget seems to be the trick, but I'm unable to get it working. The line of code we are using is as follows:

 myAnimator.MatchTarget(Vector3.up * targetHeight, Quaternion.identity, AvatarTarget.Root, new MatchTargetWeightMask(Vector3.one, 0), .1f, .5f);

As you can see, we're trying to use the match target in a very similar way to the tutorial video, but instead of using a hitPoint on the ground we're using a Y position we are calculating as Vector3.up * targetHeight. Still, the NPC isn't moving at all along its Y axis and I've become a bit stumped.

The one nuance I can comment on is that the NPC is using the Generic mecanim rig, not the humanoid. Would this make a difference? Would using a non-humanoid rig make MatchTarget not work? If so, what would be the best alternative? If not, what am I doing wrong?