For those who believe that any teams is in the F3 because they were spotted leaving the airport in Beijing, the use of decoys is standard practice in Amazing Races. Who are selected by World Race Productions to be decoys? They draw from the 6th, 5th and 4th place finishers, all of whom typically travel with the entourage of WRP production personnel. So, that means that the reported spotting of Cara/Jaime in Beijing airport does not guarantee that they are an F3 team.
Since they are already an F6 team, if by bad fortune their penalty puts them in last place or if they get eliminated in Bagkok or Guilin, they would be avalable for decoy duty.
EDITOR'S NOTE- since puddin questioned my original statement (Margie/Luke), I checked and changed it to Cara/Jaime.