dHenry,
I was going to put the shunt in the return to ground. One side of the shunt grounded. The high side would then go to the ADC pin of the chip.
My concern about the input impedance is valid as I did not want 8 amps trying to find a path through the chip rather than the shunt. Can you imagine what 8 amps would do to it. Magic smoke and fire for sure. 
The point is now moot as I have one of the Hall Effect sensors from Pololu on order to try. I like the isolation this device will provide.
I am going to need to get creative on the voltage measurement side of the project as I have two different battery cell counts. One is a 3s battery which provides 11.1 volts and the other is a 6s battery which provides 22.2 volts. I am going to need two different voltage dividers depending on which battery I am measuring. Right now I am thinking of using the balancing ports as a place to measure the battery voltage.
The 3s balancing port has a smaller connector on it vs the 6s battery so when I plug in the 3s I would connect into voltage divider A and when I plug in the 6s Battery I would connect into voltage divider B.
I am also going to have to have two different load cells for the two different cell count batteries. I plan on using 12v 50 watt halogen bulbs for my load. Two in parallel for the 3s and 4 in series/parallel for the 6s cells.
RWW