Having a total panel thickness of more than 10mm won’t really work for screw ins.
If it currently has US parts in it, then yes you’ll have to mod it.
Replace the spring with a tighter one. Also, the throw won’t become larger with time. Throw is always set. It never increases or decreases without physical modification to the joystick.
You can remove the restrictor, but it will not change the movement of the LS-32 stick. Also, TingBoy is correct in what he said.