note: if you shave the contact board slightly more on the side opposite the coil, you'll have to bore just a little less...
Anyway - 4 < 4.3? not according to match's tests.
Also, his readings were taken 10seconds after power on, and brightness during those ten seconds is my primary goal.
This will be a fair weather search light in my boat and will rarely run even 10 seconds at a time. You're not supposed to use 'headlights'...they obscure the lights that indicate your boat's heading to other boats. I just do short bursts to make sure there isn't some obstacle in my path (floating log) and to search for a spot on a distant shore.
BUT, since I'm undoubtedly not heat sinked as well it might be true in practice w/ the D1, especially beyond 10 seconds.
In any case, I prefer to err slightly higher than lower. I'm not concerned about emitter longevity, I always have a backup and...I'm sure I'll be swapping the emitter to U2, and then whatever is available next :)