Ideally, the trim should be in the middle when the engine is at idle. I do this by adjusting the pushrod so that the carb is open just a tiny bit when the throttle is back and trim at in the middle. This way I can trim back to kill the engine. Nowadays, I program a separate kill switch on the radio to do this.

If you set the throw from dead stick and open the trim to get to idle you may end up not having enough trim to open the throttle. Also if you did it that way you'd be in effect readjusting the idle everytime you fly which could mess up your day if you didn't get it just right.

Damon