If you disassemble the sticks and take the shaft to a machine shop, they can cut, turn them down and rethread, since you're taking off a whole centimeter that will give them fresh, full diameter steel to work with. You'll lose the chrome, shouldn't be a big deal.
If you find a cool old cooter machinist it would probably be $50. If its a new professional shop they won't want to talk to you.
If you are OK with the throw, you might consider spacing the joystick body down 1 cm from the underside of the panel to get your height without reducing throw.