Have you moved you low end adjustment dial yet? I have a Moki 1.80 with a Cline, Morgan FAI fuel and OS type F plug, and just yesterday was trying to tweek my low end. I could barely move it off the center tick in either direction without it being too lean or too rich. Very sensitive. A rough idle is usually a sign of the low end being too rich. But your transition is so good that you don't want to change it right? Mine won't transition perfectly yet. It's a little rich and also idles kind of rough. My transition hesitates slightly after idling for more than 10 seconds. If it doesn't idle for long it's fine.

Also, does your idle take a while to settle down once you put the throttle stick all the way down? That also usually means it's rich.

Joe