Just a little update:
It seems one of the issues with PHBG is needle sizing - they're just too dang small at the tip, which makes the atomizer/needle interface far too big for the main jets we usually run on mopeds. Biggest PHBG needle tip is 1.8mm vs the smallest atomizer at 2.6mm, which gives an opening area like 5x the size of an 80 main jet.
But, I dug through some Mikuni stuff I have, and the needles are almost identical in length, and both 2.5mm at the top, but the 4F18 that I have is 2mm at the tip. Allllmost worked at low rpm WOT with no main jet installed. Put in a 88 main (vs 77 with the W11 1.8mm Dellorto needle), ran decent on a very quick test ride.
Probably won't get a chance to do much else til end of next week.