I opened up the entire bottom of the cowl from the muffler back. Left the sides real tight.
I had a real problem with overheat and lean running most of the year. Kept increasing the openings in the front with no improvements.
Then at the end of the year, I plugged the opening on the left side (opposite the cylinder)and it seemed MUCH better.
Only got a few flights and then ran out of season. Waiting on spring to confirm but I think so.
Love the plane, flies great.