Not trying to pick a fight with you Charlie P. .... Whether or not non-metal linkage is required is a debatable topic. Quite a while ago, I asked Dick Hanson about using a metal pushrod or not and he said using a metal pushrod is fine as long as you isolate it by using plastic connectors on the ends.
Have used metal pushrods with plastic ends with no problems too . . .
No fight here. There's only so much you can fit in a post. ;-)
The reason, for those interested, is that the electronic ignition, or even the magneto, in gas engines can send "broad-wave" electronic pulses via induction into the servo windings that are then passed to the receiver. This can be glitch city (even with a resistor plug). Isolating the metal with nylon clevises is just another way around the problem. The arm of the servo also isolates it (unless you're using aluminum arms). I use Ny-rods or Gold-N-Rods. Lots of ways to skin a cat.