thats true of all the SA boxes - real pain in the butt.
I have been able to to do - though not with the SA remote - and it involves some expense.
In essence you must have a sophisicated remote control and build the the commands into it. There has to be some type of repeater system that can translate the data and you can define which routes to which in your remote control interface. Place the remote repeater xmiter in front of the proper 8300 and cover that to keep it from transferring to the other.
A real PITA.