I have been putting the profiled washer on the inside with the tube. The nuts can be locked together with a small gap from the inner rim so if the tyre moves on the rim and pulls the tube with it the valve will move over to an angle. (This won't happen on CK lawnmower engine) You can see if the tyre has moved because the valve stem is at an angle and you can then move the tyre and tube back before the valve is torn from the tube. This maybe the wrong way because I never research anything and just get on and do it.