OK, somewhere, we're doing something different. Here's the setup I have in my 9C (not super) transmitter:

Channels 1 & 6 are ailerons
Channels 2 & 5 are elevators
Channel 3 is throttle
Channels 4 & 8 are rudder

Flaperon mix is turned on to power the two aileron servos.

Pmix1: For 2 elevator servos
ON
Elev Master
Gear Slave
Link Off Trim On
Switch Null

Pmix2: Throttle to Rudder Mix
ON
Throt Master
Rudd slave
Trim ON
Switch Null

Pmix 3: For two Rudder servos
ON
Rudd Master
Aux2 Slave
Link ON
Trim ON
Switch Null

Pmix6: For Rudder -> Aileron mixing, switch activated
ON w/switch
Rudd Master
Aleron Slave
Link ON
Switch F DOWN

Pmix 7: For Rudder -> Elevator mixing, switch activated
ON w/switch
Rudder Master
Elevator Slave
Link ON
Switch F DOWN

Everything works. Now, if I've misinterpreted what we're trying to do, then I'll accept that. When I have switch F in the 'off' position, I have channels 2 & 5 working on elevators, 1 & 6 operating ailerons, 4 & 8 operating rudder. Throttle always influences rudder (not on a switch, but can be) and both rudder servos move.

When I flip switch F, moving the rudder stick moves both elevator servos, both aileron servos, and both rudder servos.

Have I missed anything?

Thanks.