For what its worth I wrote to Jeep (see attached) to provide some direction to increase or alternative solutions around GVM.
Received the following answer:
1) Refer to the Jeep website for specifications
2) With regards towing ..... consult a suitable professional
I expected more engagement/dialogue to try and see 1) if the 622kg payload is correct for the Overland with Air Suspension and 2) if correct then what can be done to increase.
Its a pity that they do not care.