Three years too late, but I have the answers.
The hex is approx 37/38mm across flats, but they were installed with Loctite when first assembled. You will need a bit of heat and some good leverage to get it undone. Hold the tap body in the soft jaws of a vice and gently warm the tap with a blowtorch, being careful not to scorch the plating. With a "breaker-bar" use an increasing amount of torque and it will break the seal that the locking compound has created.
You'll need to let me know whether you have a nylon or brass shuttle, as the pin on the cam is sized differently for each model. (unless changed as a pair)
Good luck and get in touch for more details.