Unfortunately I have never done anything with the DX7. I know there are some on here that have thought.
Pretty much, you need to set your pitch curves, throttle curves, swash type and throttle hold. Information is below.
Throttle Curves
Normal: 0 40 60 60 60
Idle Up: 85 85 85 85 85
Pitch curves
Normal: 46 48 50 75 100
Idle Up: 0 25 50 75 100
Throttle Hold (should be in throttle curves)
Throttle: 0 0 0 0 0
Pitch: 0 25 50 75 100
Swash Type
3 Servo, 90º
Hope this helps.