FORD 2009 F-550 v.3 - Manual (Page 257)

WARNING: The appropriate loading capacity of your vehicle can
be limited either by volume capacity (how much space is
available) or by payload capacity (how much weight the vehicle should
carry). Once you have reached the maximum payload of your vehicle,
do not add more cargo, even if there is space available. Overloading or
improperly loading your vehicle can contribute to loss of vehicle
control and vehicle rollover.
Example only:
2009 F-250/350/450/550 (f23)
Owners Guide, 3rd Printing
USA (fus)
Tires, Wheels and Loading
257