Increase drum speed first. If that doesn't do it, bump the airflow.

For what it's worth, drum speed will increase loft aand lift more seeds up in the airflow. This will remove chaff and might even increase your rate of rise.

Airflow increases will become ineffective as excess dilutive air decreases your environmental temp reducing available heat to drive the roast.

There is no ideal setting. Only the range of preheat, applied heat, drum speed and airflow settings that allow you to hit your roast and flavor targets with (ideally) the fewest changes necessary.