Thanks so much. Was thinking along those lines. Will give it a try and report backAluminium expands faster and more than steel, so you might get some successs by heating the crown.
Boiling water might be enough, or try a heat gun.
Additionally you could use a (plastic?) wedge of some kind into the slot in the crown to expand it -
you want to keep the localised stress as spread out and gentle as possible to avoid marking or stressing the crown.