Keep extra bones in mecanim, nothing seems to work.

I've already learned about Unity 4.3's loss of 'keep extra bones' tick box and how the workaround is meant to work but it still doesn't. Here is my process.

Import FBX containing my character and her animations. She has a ponytail and a fringe, each with their own secondary animations.

I click on the animations tab and the hair animation plays as expected when rig is 'generic'. But I need it humanoid. When I change to humanoid I notice the hair animation disappears.

Then I carry on and create an avatar mask as instructed by several people on the answers and forums. I use the imported fbx's avatar as the thing to get the skeleton from under 'transform.'

The screen fills up with all the bones included in the rig, all makes sense so far.

I go back to the animations tab of the imported fbx and choose the fist animation clip. I scroll down and under 'mask' I change it from 'create from this model' to 'copy from other mask.' Then I choose the mask I just created.

I check the preview window again and the hair bones still aren't being animated. I set up a quick animation controller and put the first animation in as the default one and press play in the hope that it'll do what I want at runtime, but it doesn't.

In an attempt to see if the mask is affecting anything I untick EVERYTHING in the avatar mask I created but it makes no difference whatsoever. I would have expected the animation to... not move at all...

Could someone let me know what's going wrong here please? I haven't got a clue on this.