Issues making one rig follow another

I’m trying to make a rig for the character’s hair follow the rigify body rig. I’ve tried using bone constraints (Child Of, Armature, Copy Location etc) but nothing works the way I’d expect - when I add the constraints, some of the bones go where they’re meant to but others either stay put or jump wildly out of proportion. I think it’s a parenting issue within the hair rig itself, but changing the parenting in there breaks the entire hair rig, so I’m just stuck. I followed this tutorial to create the hair rig (he talks fast and doesn’t explain much of his process so I would not be surprised at all if I missed steps and that’s what’s causing the issue here).

Would anyone be willing to take a look at the rigs and see if they can pinpoint where I’m going wrong? Thanks in advance!

Google Drive link to the file since I’m a new user here and can’t upload attachments yet.

EDIT: If it becomes relevant, I just realized there are some vertex groups from a previous hair rig that doesn’t exist anymore. Those groups are called ‘Hair Strand’ and can be ignored. The groups relevant to this current rig are just called ‘Hair’. Sorry about that.

You have to parent the Hair rig to the Head bone of the Shev rig…

I turned off the constraints, as the tail entered the body, since it is so far down

Thanks for your help! I see that what you did worked in the file I provided, but I can’t seem to replicate the results in my actual file. The file I linked in the Google Drive had most of the stuff deleted because my scene contained a lot of other meshes and materials that would have slowed it down a lot. Would you mind explaining how you got it to work in a little more detail? When I parent it to the head bone, it does this…

Very simply, in object mode…
Select Hair Rig, shift select Shev rig…
Ctrl + P, and select BONE.

Make sure to disable the constraints, and you are in Rest Pose…

I checked many things, so I am not sure if this covers everything, that’s why I included the file…