You need to create two folders in the Airplanes directory where GSX Pro is installed
C:\Users\xxxx\AppData\Roaming\virtuali\Airplanes
folder names :
inibuilds-aircraft-a306f
and
inibuilds-aircraft-a306r
then copy the gsx.cfg file contained in the directory where the aircraft are installed "inibuilds-aircraft-a300-600\SimObjects\Airplanes".
Note that the names of the aircraft configuration files are identical, so make sure you put the gsx.cfg for the f and r versions in the correct Virtuali/Airplanes folder.
André