Sincraft:

Get it running at full speed, peak the HS needle. Down to idle, pinch the fuel line. Adjust the LS needle until the pinch gives a slight rise in rpm before falling off with the pinch. Go back to full and set the HS where you normally have it for flight. Now back to idle for a moment, then go to full. If the transition is now clean, leave it alone. More probably it will sag a little, so open the LS a bit and recheck the high speed - the two needles will interact a bit - and recheck the transition.

Can be a bother to get it right, but once it's there you might never have to touch it again, unless you make a large change in the fuel.

Bill.