i will tell you this, the holes you want to slot are the ones that the holdong screws go in. now in the past i have played games w advancing and retarding timing on kx's, cr's, and such.
but what i have found is,(at least in my case on 2-stroke racing bikes) is that just retarding the timing alittle lets the bike run smoother and i can change my gearing to compensate. and it obviously helps the over rev alittle and lets the motor run alittle cooler. (hotter pipe)
now to answer you question, when eric gorr says not to go beyond .7mm. I THINK, I'm not 100% on this but i think you can measure that distance from the center of your mounting hole and file no further than .7mm in both directions. not sure on exactly how to measure this, but i make sure i just do alittle at a time.
another thing you could try is seeing if the yz's use a similar stator plate, b/c those are adjustable. just a thought.
sorry if this doesn't answer your question, but hope it helps. :cool: