Actually, the 7C's Pmixes are rather simple, once you understand how they work.
First, enter the first mix. Change the "INH" to whatever comes up. It will say "ON" or "OFF". Go to the second page of the mix and select which channel will be the master and which will be the slave. For the dual ailerons, channel 1 will be master and channel 6 will be the slave. Since you want the mix to be on all the time, set the "SW" to "--". That means that you are not using a switch to turn the mix on and off, but having is on all the time.
Return to the first screen. Move the stick to the right and one of the "%" symbols to the right of the "RT" will flash. Adjust as necessary to have the slave channel move as desired. Move the stick to the left and you'll see that you can adjust the other number. They can be set to a "+" or "-" percentage. That only means which way the slave channel moves when you move the control stick.
For elevators, you'll get channel 2 set up the way you want and then go through the same steps for channel 5, except you'll move the elevator control to set the mixing rates (RT).
One thing to remember with the 7C is that the aileron trim will not affect the slaved aileron channel, nor will the elevator trim affect the slaved elevator channel.
Don't worry about "OFS". That means "offset", and is used to move a channel to a fixed position when you turn on the mix.