This is an interesting discussion. What I may have missed is: Is the spring there only strong enough to return the carb to idle if the linkage falls off? Is the spring strong enough to return the carb to idle working against the servo gear train with no power applied to the servo? The reason I ask is the comment that lightly forcing a control surface from its detent position with the system up and running or lightly moving a servo till it buzzes will raise current levels well above that of a servo fighting the carb return spring. this makes it sound as if the return spring can only help you in the event of linkage disconnect and not servo failure.