Yeah I think Frogboy is right... but the chance of getting a slotted mid headgear is next to nothing so if someone actually gets one, don't they deserve a hax reward?
Anyway, I kinda want a Myst Case Hat slotted with a Myst Case Card....
Maybe in the event of special rare-drop hats like Myst Case Hat, the stats go down when you slot it?
Gravity does this all the time, e.g. making an Earring[0] lose 1 int when you socket enchant it into an Earring[1].
Maybe for Myst Case Hat, when you socket enchant it, it's Mammonite bonus decreases down to 10% or 5%? I think that would make a lot of sense