First I acknowledge lianpinkoh's post, "Channel Mixing in Turnigy 9XR for Arducopter/Arduplane" as this was the post I started out with. The method I explain below is only a Modified version of lianpinkoh's that is more taylored towards arduplane rather than arducopter and that does not require the servo cable to channel 7.
Below are the uses for the switches I am using:
This Mixing schedule (shown below) sets up the three switches shown above to do the following:
1.) The switch on the left will return the Aircraft to manual mode(mode 6) no matter what mode it currently is in. Think of this switch as activating/deactivating the other two.
2.) The Middle switch is a three position switch and will switch between three different modes.
3.) The switch on the right is a two position switch. This switch changes between one set of three modes and another.
If the left switch is flipped up, the 6 modes are activated as follows:
Mode 6: Middle switch: Down, Right switch: down
Mode 5: Middle switch: Middle, Right switch: down
Mode 4: Middle switch: Up, Right switch: down
Mode 3: Middle switch: Up, Right switch: Up
Mode 2: Middle switch: Middle, Right switch: Up
Mode 1: Middle switch: Down, Right switch: Up
Again, if the left switch is flipped down, the middle and right switches are ignored and the aircraft will return to manual mode (Mode 6 in arduplane).
Connect receiver CH6 to APM CH8 for arduplane.
Let me know if you have any questions!