Even with motor_stop disabled and pid_at_min_throttle active, CleanFlight 1.9 doesn't hold attitude effectively at zero throttle because it zeroes out the I term in order to avoid windup when the copter is idling on the ground. I took a suggestion from RCGroups and set up an "idle up" switch on my copter. The switch holds the throttle at zero when it is in the "safe" position. After using the stick to arm, the switch is flipped, which causes the throttle to work as normal, except the throttle curve stops just above min_throttle (or min_check, if your min_throttle is below your min_check). As a result, the FC never resets the I term when the copter is in the air.
