I finished off the last of the 10% oil mix, drained the tank and filled it with the 15% mix, opened the needle three clicks (didn't touch the reg) and tached it at at just over 7.3K. I closed the needle one click and the tach reading didn't really change, so I put the belly pan back on and didn't touch it for the rest of the day.

Smoke was pouring out like a steam train at high power settings and the oil under the plane was slightly darker than it was before, so I'm guessing I was still a bit rich when running the 10% mix... or is it I'm a bit lean now???... with the YS it's hard to say.