RE: throttle return spring ?
My OS 46 FX-H is set up this way as well. There is a spring in the carb that pulls it to full throttle.
Who's idea is this? On any model application this just seems dangerous. Be it a plank, a car or a heli. When the linkage comes off the engine should return to idle, at least IMHO.
I personally find this very unsafe, as the linkage is likely to break or come off during a crash.
Is it possible to modify the carb to take out this spring?