Unfortunately I did not have a working manometer at the original time of testing to perform Pressure Drop testing on the RX120. I am once again armed with a working and much better manometer (specifically made for liquids) as I write this, so pressure drop testing will be added during the testing of the RX360. Sorry for the inconvenience.
When building your loop there should be a list of things that come to mind, flow and pressure should be near the top of that list. Pressure drop is the measurement of inlet pressure minus outlet pressure, or the pressure lost of flow through the radiator.