I'm not sure on a Futaba but I think its the same, as on my airtronics
The master is really the radio that has the same crystal as the reciever
in the plane... If both of your radios are on the same frequency, either
can be the master, the slave/buddy box has to be off with the ant. down
and the sticks and trim get activated on the slave as you push the trainer
switch on the master... On the dual rates... I'm not sure, but I would think
they may work... But why??? If their ready for dual rates, you don't need
the buddy box...

Make sure all the controls match the plane... I.E. with the master and
plane on, sticks centered(same stick position on both radios).. activate the
slave/buddy box the controls on the plane should remain in the same
position with the trainer button/switch pushed or released...