I'd be willing to bet most guys are just mounting the throttle servo near the engine WITHOUT using the fiberoptic extensions. They are running the risk of introducing rf noise into their system. You'd probably be amazed at the way some people set their planes up, it's a wonder more of them don't crash. How about the guy who has radio intereference on ppm and says "I'll switch to PCM to avoid the problem". I think that fiberoptic extensions are great. If you choose not to use them mount the servo at least 12" away from the throttle. In fact it is a good idea to separate all engine componets from the radio components.