I checked the case hole again, the washer OD is 27mm and the case boss flat surface area is 30mm OD.
The washer is just 3mm smaller in dia. than the boss or 1.5mm each side. Yes, WERK-I, the washer is just the right size.
The fitting hex needs a 32mm socket.
The fitting hex nut in the tubing needs a 36mm wrench.
