Not sure that your system of having a head with the neck as child will work for a conformer. I think it has to be rigged with the same hierarchy as the target figure. That is to say with the head as a child of the neck.

All the conforming hair figures I have see have the hair geometry in the neck actor, and the head is a child of the neck. There is nothing that I know of to stop you having geometry groups for other parts, like the head or chest, though this is not usually necessary unless the hair goes below the chest actor. But I think the hierarchy needs to be the same as the target figure (I may be wrong).