It seems the OP's question is answered, but here is my logic for installing the current shunt differently.
There are several acceptable positions to install the current shunt. I installed mine to measure load demand to the battery/alternator. This means that I do not measure the full current draw of the alternator, so I do not know the charging+usage amps, just usage. I figure that as long as the voltage is 14.0+ 0.2 volts, then the battery is getting it's charge and not a worry. If the alternator goes out then I know the amperage draw on the battery as measured by the shunt and can reduce loads while monitoring the voltage. The back up battery(s) can be added to reduce the starting battery load.
This is my logic, and yours can be the opposite and still be "right".