I buddy box the Futaba 2.4GHz with a Futaba 72MHz unit with no problems. One odd characteristic though, when you switch the master (the 2.4 GHz unit) over to the slave, there is a lag between the time you throw the switch and when the 72MHz unit takes over, about .5 to 1 second. Going the other way (taking control back from the slave) is instantaineous so it is not a problem but was disconcerting the first time I used the buddy box. In contact with Futaba, they said this was normal. I suspect this is also true with the Spectrum but have not tried that yet.