Mecanim problem

Hi,

   I have a Humanoid Character which is animated in maya with a Cricket Bat, and the Bat  is animated as well with the character (it has attached with the character rotation portion). I use mecanim system to handle animations. The animations are fine in unity. I can use Generic and Legacy rig setup and it works perfectly with mecanim.

The only problem is when I want to use Humanoid rig setup the Cricket Bat transition always incorrect. It's problem depends on the cricket bat position in the source avatar definition I use.

So how can I handle this problem if I want my character to use Humanoid rig?

Thanks.