yeah i spent a long time getting my 14/12 drilled to a 16.something to work just right, but once it was dialed in, it rocked. I think i had drilled the idle hole up 1 or 2 wire gauges, the half throttle hole was drilled up about 3 or 4 wire sizes and the slide is cut with a round notch in the middle.
still i'd rather have the bing, chucking the needle in a drill and turning it with some sandpaper has resulted in some of the best running moped engines i've ever built. it seems like you just cant get the midrange dialed in as well with discrete holes, as you can with a tapered needle.