I was told that if you tighten it down to the right setting, it will keep the carb. from closing past idle, in effect keeping the engine running.

I don't know anyone who uses it for this, for two reasons, as stated above, unless your radio is very precisely set up, it could easily cause the throttle servo to bind (draining your RX battery) and also because most people prefer to be able to kill their engine by bringing the throttle trim down, which is exactly what it would prevent.