You don't specifically mention the radiator itself, probably because the term is less appropriate with this design - am I correct in assuming that the path from the stock pump outlet to the flow meter is what spreads the heat from the water to the fins (essentially is the radiator)?The in would most likely be straight from the reservoir since the stock setup has the output from the stock pump feeding it's output straight into the flow meter then out to the PC.
So knowing that the most important detail is the reservoir/pump connection, the ideal setup with an external pump and the stock pump removed would be:
R2 IN >>> External Pump >>> Water Blocks >>> R2 OUT
Yes? Nothing funky in the flow meter path when flow is reversed?
Just trying to wrap up this guy's question.