Update,
The boss was rubbing quite hard against the raised collar of the steering column housing. So I ground that down (the housing, not the boss). The boss is now rubbing on the face of the housing slightly, and making a bloody annoying creaking sound when I turn the wheel. So going to go ahead and take a bit off the boss with the belt sander.
Also the two pins on the bottom of the boss that are supposed to cancel the indicator are set too wide apart. They are set at 33mm between them, and the blue plastic part with the slots cut in it that they are supposed to locate into, is only 30mm outside diameter. Solution for me was to bend the pins inward. Works perfect, but why are they made like this in the first place?