FORD 2012 Flex v.2 - Manual (Page 122)

WARNING: When loading the roof rail crossbars, it is
recommended to evenly distribute the load, as well as maintain a
low center of gravity. Loaded vehicles, with higher centers of gravity,
may handle differently than unloaded vehicles. Extra precautions, such
as slower speeds and increased stopping distance, should be taken
when driving a heavily loaded vehicle.
When the rail system is loaded, check the tightness of the load before
driving and at each fuel stop.
Driver Controls
121
2012 Flex (471)
Owners Guide, 2nd Printing
USA (fus)