Outside wheel for me, too. I wait until the track is clear, then set the car parallel to one wall, touching it, do a half circle, then set my foot up against the car, marking the spot. Then repeat going the other direction, adjusting the EPA for the same circle going right or left.

It's always best to describe the amount of steering throw you are using with a turning circle as opposed to some percentage of adjustment on the radio, since the percentage depends on the radio, servo, steering linkage, and wheelbase-- all of which vary from car to car.