we use an extremely simple drive circuit.

It might look complicated, but the essence is dead simple.

Each light has 21 LEDs connected in 3-parallel-7-series configuration. The driver for each light is just a 0.5-ohm resistor in series, a mosfet that turns on for the whole duration of the pulse, and an energy storage electrolytic capacitor to prevent voltage drop along the rather long and thin power supply wires. The constant voltage on that capacitor can be adjusted to adjust the pulse current; there is otherwise no active regulation of current going on.

The voltage drop across the whole light at low currents (0.6A/led) is around 20V. The capacitor is at 40V, and at 18A, the voltage drop across the so-called "current limiting resistor" is 9V. So the light gets 31V, which is 4.42V / LED. It seems that at higher currents, LEDs become more resistor-like, and that this "current-limiting" resistor isn't doing very much. It seems that it can be removed altogether, though i'm a bit scared to do it.