Scoubi,

Whenever I have a ball link that's not captured, as in the middle of a clevis, I like to add a flat washer over the top as a fail safe in the event the link gets rocked over so hard the housing pops off of the ball. If that happens, without the washer you're well and truly screwed.

The older Dubro links were quite prone to this. The newer ones are almost a direct copy of the RCL 70 ball link, and are MUCH better than they used to be. The JR plastic housing ball link is another that is more or less a copy of the RCL link, and well made.

So, places like the link to servo arm assembly on an aileron, rudder, or elevator servo is where I add a flat washer. With a clevis it's not needed, or really possible.