Just to clarify, you can have only one boot release from the OB4 double boot system in some instances, but if there is any rotational force or dragging on the ski that would cause any injury, the second boot would also release once your release setting was exceeded. Resulting in no injury!! That is the point anyway... @kfennell is correct...
Also of note, I have skied all summer with no problems from the original bolt/washer setup. If you need it, try @Than_Bogan setup...or Loctite, seems the screws may work loose from flexing of the boot... Also I have other solutions if needed.
@Edbrazil thirty years behind because there is thirty time less money in water skiing...