I'm in need of a clarification regarding the Vivitar 2x teleconverter. On the S2 and S2a, the lens and helicoid come apart, so you remove the helicoid, mount the 2x into the body, then the original helicoid, then the lens. It seems that on the S, the helicoid and lens are one piece. Is the rear of the S helicoid the same size as on the S2 and S2a? In other words, can the 2x tele be mounted on the Bronica S?

Any information would be very welcome.