If you use a LED, 4 diodes could be too much.. Need to measure..
But a CREE LED (or any white LED) will have a Vf of around 3.5V anyway.. So if you use a LED capable of taking high currents, you don't even need a diode in series, but put one or two there anyway. The exact Vf is unimportant, as long as it is in range.
The Vf of the dummy being close to the Vf of the diode only matters, when you use a linear driver, which needs a certain voltage on top of what the load needs.. So there you might want to simulate the right conditions, where the input voltage requirements depend on the output voltage requirements.
With a buck/boost driver, the input voltage doesn't depend on the required output voltage - it just has to be within the input range. And as long as the dummy Vf is within the output range, the current WILL be the same as later with the diode.
You can either put the DMM in the current measuring range (2A or more, but for PHRs, 200mA is also good), you have to use another socket for this, so that current can flow THROUGH the DMM, and then you put the DMM BETWEEN the driver and the dummy load.
The other option, which i mentioned before, is to put a 1 Ohm 1 % resistor in series with the dummy load (i make this resistor a part of the dummy load), and use a low voltage measuring range (2000mV = 2V). Then you measure the voltage on both sides of this resistor. Voltage ACROSS a 1 Ohm resistor in mV is the same as the current THROUGH it in mA.
Hehe, sorry, i was just confused from all the talk about the dummy load.. ;D
But the driver is tiny, and if you mount it flat on the depopulated battery contact PCB (use some insulation in between!), you'll be fine.. If you can't use the back of the AixiZ module, don't.. Just use the head, but make sure you have some aluminum around it.