You like to challenge the brain in the morning, but I think you are correct. Due to the taper angles/profiles being the same, when working back from the pointy end the diameter will also have an effect on the length of the straight section and where it comes into the taper. From there however, the thicker needle is also tapering where the other needle is still straight and due to being such a small area its near impossible to measure in any accuracy.
A much larger variable is the diameter itself as it occurs over the entire straight section (closed until when it picks up the taper). That means as the slide lifts for that entire duration the fuel mix will be leaning off until it comes into fuel (the taper). Lifting the clip increases the straight section that is in effect which is why I noticed it most in that 1/4 throttle range (although it does effect the whole of the range).
Then you introduce the pilot and (air screw) which overlaps the straight section. I use this soley to set up the idle in conjunction with the needle diameter, and the air screw in the sweet spot 1.5-2 turns out.
Soo....
From what you have determined
1) N3Ex #2 is too lean on the needle (too snappy)
2) H diameter and 40 pilot is too rich (blubbers down low - small openings but idles - idle mix seems OK but rich on the needle)
3) W diameter and 40 pilot is too lean (hestiates when cracking - how'd it run at part throttle?)
My next step is exactly as you suggested, work with the 42 pilot and W diameter. You may find yourself jumping one further and even going 45/J for the best repsonse.
Interestingly though, you're going through a similar process I did on my 2013R after the head mods. No cracking issues on the pilot for me though as even a 40/W combo has me running 2.5 turns out on the AS (on a 250!!).. But the N3Exx was too flat/flat out transitionish at clip 2, and just too rich at clip 3. I moved back to the Suzuki needles, and ran it in clip 2. Gave a similar off the bottom as the N3Ex#2 with a mid to top similar to a N3Cx#3.. Kind of best of both worlds.
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