John, I think you are at least half-right!
There appear to be two hex files that control the appearance of lightning in the game. EnvSim.act, the file I believe you are referring to, seems to control the
graphics associated with lightning flashes and other environmental variables such as sea and sky color, etc.
Scene.dat, on the other hand, seems to control the positioning and timing of lightning flashes. Strangely, though, I can't get Silent Editor to open the file, so I can only see it using a Hex editor. I have highlighted the lightning section, but there appears to be only two values that need changing, MinTime and MaxTime.
