Speaking of mounting servos....................

You know they almost all come with metal "top hat" inserts. And the majority have tiny washers while the ones that don't come with those washers have screws with "washer heads". There is a reason for all that.

Almost all servos are mounted with rubber inserts. And those top hat inserts and washers have a definite purpose.

The top hats are supposed to be inserted from the bottom of the rubber insert. Basically, the servo winds up sitting on 4 top hats. The "brim" of the top hat acts as a washer that allows the mounting screw to be tightened until it contacts the "hat" or tube of the top hat. The mounting screw is to be tightened until it presses the top hat against the wood that the servo is mounted against, or until the rubber is compressed as much as you wish. The tiny washer or large screw head is there to compress against the rubber insert.

When the screw is tightened until it contacts the top hat, the rubber insert is securely captured and held. The top hat insures that the servo isn't mounted too solidly. It's hat brim insures that the top hat isn't driven into the wood, as it would if the top hat were in the rubber insert the other way round. The top hat insures that the screw perfectly tensions the rubber insert. That is, it does if it's in the insert the right direction. And if the screw is tightened enough that the rubber is compressed.

That top hat also helps keep the mounting screws tight. If all you had was the rubber insert and a screw, the screws would have rubber pushing against them continuously, in a loosening direction. And with the vibration of the airplane, they just might loosen up until the servo wasn't mounted securely enough to keep from rocking. And you would certainly would have less precision from that servo. Is this something to worry about? No more than about the degree of accuracy you're going to lose from rocking. When you've developed enough experience that you can appreciate absolute servo accuracy, you'll also have a good feel for all these other details and their actual impact.

You can usually tighten the screw until you see the rubber insert compress. Almost everything in our hobby requires learning some technique. Getting the rubber insert compressed very slightly is one. And not every technique is really very important.