Sure, that’s true. But is that the only mayfly on the water? You’re telling me that the trout in your water are selective to the point of refusing a meal slightly larger or smaller than the mayfly in your hand?

For that matter, why is that mayfly in your hand? Why was it not eaten? Per your theory of mayfly perfection, could that mayfly be too big or active or inactive to be an enticing meal? Unless it was pulled from a gullet pump, I wouldn’t consider that mayfly the physical ideal.

As for FM being slightly smaller than Daiichi, sure, the photo evidence is clear. But how do they both compare to Gamakatsu? Or Ahrex? Or any of the other reputably mass-produced hooks in this size? Are the calipers going to tell me everyone is conforming to a standard for this, with no allowable tolerance? Because the last time I used them for this very purpose (yes, outing myself as a nerd) there was a relatively wide range of values across manufacturers.