Question ARKit face tracking for a helmet object

Hi,

I am trying to place a helmet on face tracking. Something like this. Tried the helmet model as a face prefab, but it was placing over the face and not as shown in the video. Anyone could suggest how do I proceed this?

I was thinking of getting the center point of the generated face mesh prefab and place it a little offset behind it to center the helmet over the head. I am not sure this would work.

Any help is appreciated.