This is how it worked for my DX7,
I use various switch combinations of the FLAPS and the GEAR switch which will give you 6 modes;
(note that you have to use the DX7 in "airplane mode", not in "heli mode" to fly a quadcopter)
- Press SCROLL DOWN + SELECT to access the programming mode
- Go to the "Travel Adjust" menu with the SCROLL UP/DOWN button
- click the SELECT button till you reach "Flap", then set "Flap" to "U 65%" and "D 65%" (INCREASE/DECREASE button, you'll have to move the "Flap" switch to select between "U" and "D", this means put the switch in "N" position (away from you) to program the "U" value and move the switch to the "2" position for the "D" value)
- Leave "Gear" on 100% - 100%
- Go to "Mix1" (with the SCROLL UP/DOWN button)
- go into the menu of "Mix1" by pressing the INCREASE button
- Select "Ger" > by pressing the INCREASE button
- press SELECT to jump to the second position and elect > "Flap" on by pressing the INCREASE button
- press SELECT
- Set rate to "19%" and "31%" (with the INCREASE/DECREASE button, you'll have to put the GEAR switch in the "0" position for the first value and into the "1" position to set the second value)
- press SELECT
- Set SW to "on" by pressing the INCREASE button
- Leave Offset at "0"
connect now your APM to the Ardupilot Mega Planner, go to the setup page and assign different flight modes to the switch combinations of your remote.
I like to have easy access to the simple mode (just to get very quick out of a difficult situation) which is the reason why I have two switch combinations programmed for simple mode. I have set it the way that simple mode is selected if the "Flaps" switch is on "N" (away from me), no matter if the "Gear" switch is on or off. This way I have just 5 modes accessible, but I can very easy and quick switch back to simple mode.
(this is based on the blog post by Nick Wadman, I just adopted the programming description for a DX7)