Is it not possible for SF to use a different regulation circuit like the one that is used in the L6 to take 3 batteries? This way we could have a more versatile light and choose either a 2 or 3 batteries configuration by adding or subtracting A19 extender or the likes in HAIII.
If SF used the L6 driver in the KL5, it would work great on 3x123 and be a dog on 2x123. One is a boost circuit (KL5's) and the other is a step down (buck) circuit (KL6). The only combo buck/boost circuit in SF's current lineup is in the KL1.
What Don said - And you may then ask: Why not put in a buck/boost circuit like the one in the KL1? The answer to that, I think, is that such a type of converter can't be made as efficient (yet), so runtimes would be rather low. Am I right Don?