If you have to zoom your scope out to acquire targets and then zoom back in you are lost. That is not how you acquire targets. Acquire the target location with the naked eye, point the muzzle at it while still looking at it with the naked eye, and then move your head into position behind the scope without moving the gun. The top pros do this even on higher than 20x with instant target acquisition. If you can't do this then you just haven't practiced it enough. For 99% of PRS stages you should select a magnification setting before the stage and never touch it once the clock starts.