This may be related to a discussion I was having with @kuspower in his thread. You may not notice a big difference in the response because of the ATC_ACCEL_Y_MAX. If this is really low then the aircraft is limited in its response. The default of 27000 is really too low for helicopters as I have learned recently. I believe this is more like 60000 to over 100000 depending on the helicopter. Be careful as you raise this as it can mask the instability due to high rate P or rate D gain values.