An engine generates power through rotational force, not fore/aft forces. Although a propeller does impart minor fore/aft forces throughout the combustion impulse process, those forces are negligible as far as a throttle servo and linkage are concerned if the engine and servo are secured in and on the fuselage.

Most people destroy a throttle servo though incorrect linkage travel. I have seen many throttle linkage installations where the linkage was both too long for the application with the servo driving both itself and the carb linkage hard against the stops. As mentioned before, I have seen JR 8611's, 8711's and Hitec 5975's destroyed in only a few flights by improper linkage geometry. One servo had pretty much torn itself out of the plywood it had been attached to because of excessively long linkage and a servo at more than 100% travel. That one was the epitome of stupid, and installed by a well known competitive flyer.

I ONLY use rigid linkage, generally of carbon fiber tube material, and typically using a straight shot to the carb. Flexible linkage brings with it problems associated with a creeping throttle as temperatures change throughiut a day. Ends are attached with at minimum one ball link but typically one at each end. Neither the servo or the carb linkage EVER hit the stops. There's no reason for that to happen because a gas carb achieves full power long before the throttle plate is 100% open. The last 25% of throttle plate opening does virtually nothing for RPM performance.

Excessively long linkage mulitplies the mass of the linkage times the vibration amplitiude of an engine, which is quite hard on any servo. That becomes a vertical pounding on the servo output shaft from the end of the servo arm. Under those conditions a flexible linkage could be a better choice as long as the linkage was secured for as much of its length as possible. Of note is my not having seen a plane that needed gasser throttle linkage much longer than 8". One only needs to be a little creative and not settle for using the mounting cut outs provided by kit manufacturers. Most of my linkage lengths are between 3" and 5" in length. Some as short as 1".