I've replaced all the playfield rubbers on my 1965 Gottlieb Kings and Queens except the rebound rubber. The shaft that holds the rebound rubber does not seem designed to come apart from either the front or back side. (See attached photos.) The diameter of the hole through the rebound rubber is less than half the diameter of the "bolt head" that you see in the "front" photo, what would be visible while playing the game. It occurred to me that the rebound rubber might slip over the "bolt head" part, but given the difference in diameters and the hard rubber composition of the rebound rubber, I thought I'd better ask before turning this into a muscle job. Can I replace the rubber or is the whole metal mounting assembly (along with the rebound rubber) meant to be replaced as a unit?