The Load consists of two 50 Ohm power resistors in parallel. Each dissipates 2.88 W of power as heat. The resistors are rated for 5W. Regardless, I added a radiator that I already had. This spreads the head around and prevents the parts from getting so hot that I would burn myself.
To find the right configuration that provides stables voltages within the proper margins required some experimentation. Care was taken to waste as little energy as possible.
Ohmic losses cannot be neglected. In particular when cheap PSU's are involved. On the left is an example of really thin cables. Compare to the ones on the right.
Combining six of 5V lines into a single strand, rather than using just a single line to power my RaspberryPi, resulted in an increased voltage at the RPi of 0.2V or so.
Further measures I needed to take to make the RPi work reliably was to shorten my USB-A to micro-USB adapter cable. This yielded another 0.1V or so.