Use the Navigation Lock feature to lock your sketch into one place.
Lock/Unlock the Sketch
1. Hold the Grab trigger on your non-drawing hand and the feature will appear on the non-drawing hand joystick (history button)
2. To lock the sketch simply move the thumbstick down. When the Lock is set you won't be able to resize the sketch.
To unlock squeeze the Grab trigger on your non-drawing hand controller again and move the joystick in any direction.