I have always set up actuator arms as to where I want them to track on the belt ...either further east or west. Never really gave the positioner a thought relative to south, other than to make sure the dish could make it to the eastern and western most satellite I was after. Also you NEVER want the dish to be able to "flop over" on the mount.
In my location the arm is almost 1/2 way extended when pointing true south. My true south is 119d. I start with the arm retracted and the dish at a point a little east of the furthermost eastern sat I am after
Hope this helps
Jeff