Yea verily, the answer has been revealed!
Whereupon the time of the Summer Solstice had arrived and the attendants of the holy sepulcher of Rover knowledge, known as the Dunsfold Museum, revealed the truth unto me. Said they: Thou must taketh the sacred emery cloth ... not too coarse and not too fine ... and wrap it about the holy adjustment dowel. Moveth the dowel into and out of the bushing in the manner that the newlyweds consummate their union. Do so until there is a pleasing, sliding fit to the entire assembly. We rejoiced in their wisdom. Remember, follow not the false prophets of Rover knowledge, for there are many. If you do so, back ordered parts shall haunt you the rest of your days.