chris, the throttle stick should NOT shut down the engine...if it does I hope you have better stick control than I do

with the the throttle stick all the way back the trim slider should be set so the engine idles nicely, the trim lever should shut off the engine when it's moved all the way back ..unless you have a throttle cut switch. adjust the throttle linkage/throttle servo arm so you see no opening at the carb barrel as your looking down the carb mouth with the transmitter throttle stick all the way back and the trim all the way back, now move the trim all the way up and see how much opening you have on the carb barrel, should be about 1/8 inch or so. now check that you have full throttle by moving the throttle stick all the way up, also make sure your servo is not stalled/buzzing when your at full throttle, if you have end point adjustments it easy to adjust..if not play with the linkage/servo arm placement until it's no longer stalling at full throttle. now with the trim slider up and throttle stick back, start the engine and adjust the trim until you get the slowest STABLE idle possible, you should now be able to pull the trim back and shut down the engine.
John