Here's the deal. Lightning "fires" in pulses. There is a pre-flash, then the main bolt, then depending on the potential of that cloud, the resistance of air, the pollution, rain, humidity, pressure, blah blah blah.... additional pulses. The timing from the pre-flash to the main bolt is ~30ms. And CHDK capable cameras simply cannot detect and react in that time. Consider yourself lucky if your camera can reliably do 130ms.
Most cameras with fast MD implemented do better than 130ms.
FWIW,
I live in an area where thunderstorms are rare, and generally not intense, yet I have had pretty good results with CHDK MD. IMO, the low intensity suggests the "lucky shot triggered by a previous strike" is not a major factor in what I've seen.
CHDK MD won't capture every strike, but when everything is working correctly on a port with good MD response, you can capture a decent number of strikes, in daylight with a relatively short exposure, with no additional hardware.
