I cannot help you much with the jets numbers thing, but, some bikes do allways "stutter" on the small throttle openings. it´s just the way they work.
sometimes reeds (like the boyesen, or stock but new) had cured long time jetting issues on the small end. advancing the ignition timing when possible help somewhat as well... high performance exhaust tend to increase the dificulty on low end jetting.
usually that kind of stutter may come from rich or leaner mixtures but most of the time its rich mixture. doesn´t hurt to try the 40 slow jet... try to move the needle up as well to see if it helps. at quarter throttle i find the most dificult to attain smooth running since the low speed, the needle and the cutway overlap a lot.