On the DC 8 I would go with SW1=Off and SW2=Off and Sw3=Off. This will means everything plugged into the DC8 will be referenced as A1 thru A8. On the DC4HD I would go with Sw1=On, Sw2=Off, Sw3=Off and Sw4=Off. This means everything plugged into the DC4HD will be referenced as B1 thru B2. You can play around with it however you like, just make sure the same letter number combination are used on both.
That should be it.