I just received an E-Series KL4 Head Unit (Gen 7), 1 Mode (3.7V-9V) from Lumens Factory for my LX2 Lumamax, which according to the description is also compatible with L2 and L4.
Mounted on my LX2 Lumamax, the Lumens Factory head works flawlessly at both brightness levels via the "gas pedal"...