Steve,
First thing you have to do on the T6XAS is move all the dual rates to one switch. This free's up the ELEV DR switch and now can be used for Programable Mixing (P-Mix) Doing this also ENABLES the Rudder dual rate that you dont have till you move all the DR's to one switch. ( lots of people dont know you can get Rudder DR on this radio ) To do this go to your PARA function. Once that is displayed use the cursor to move to the DRSW menu you will probably see a 1. If so, hit both + / - keys and change that 1 to a 2.
Now when you go to the DR menu you will now see 12 4. meaning that you now have a rudder dual rate. (#4)
Once that is done the ELE Dr switch is now used to control on and off for P-Mix. You need P-Mix to get spoilerons.

Set P-Mix1 to this,
Master #2 Slave #6
chnge the + or - to get the moving aileron up with up elev. Only one aileron will move at this point.

Set P-Mix2 to this,
Master #2 Slave #1

Then adjust + / - to get it going up also with up elev.

As far as the percentages to use for spoileron its hard for me to say what you need. Start with 50% and adjust after flying it.

Keep in mind that the 2 to 6 mix (flapperon) has to be off for the spoilerons to work. That seems to have priority.

Clear as mud?

Its pretty easy once you see it done.
let me know if that works for you..