Implementation of the wildly documented Inverse Square Root Magic Number refinements?

Any implementations out there use this bit of information about the Quake 3 sources?

Namely changing the famous Magic Number from 0x5F3759DF to 0x5F375A86? Or the 2 line of codes “fix” that invariably give better inverse square root guesstimates?

I’d be curious to see what it would do to the in-game lightning seeing as it’s described as such a crucial piece for the lights.