Exactly how little mudguard you need forward of the light is left as an exercise for the reader
I spent a while riding with a mudguard that had broken off at the fork crown, and my own front wheel spray got high enough to get on my glasses. To keep your own spray off a fork crown mounted light, you probably need a front mudguard that extends to about 3" or 4" in front of the wheel axle (depending on clearances).
I'd suggest that the long Berthoud mudguards are about right.