I am impressed by so many skills and knowledge together !
Thank you to Machinbird, Owain Glyndwr, Chris Scott, Brian Abraham, Hobo, PJ2, misd-agin, and others. I apologize as I need a littler more time to answer...
It seems that Harper-Cooper scale is generalized with US aircrafts, but nothing else with Airbus unless due certification is done in USA - and it seems it has not been the case with the A300-600R modifications, according to the APA document. A european manufactor test pilot is not independant to rate their own aircrafts' qualities.
A question about Harper-Cooper rating : is it done with and without Yaw Damper on ?