ORIGINAL: goirish
Are the channels on the DX-7 the same as on Futaba i.e., channel 1 ailerons, 2 elevator, 3 throttle, 4 rudder and etc.
In the reverse menu it will actually label each channel with a channel number as well as the name. i.e.: ele, rud, ail, etc.
Elevator is channel 3.
The receiver is also labeled that way as well.
When you are in the reverse menu, use the select button to highlight the function you want to reverse then use the increase/decrease switch to reverse it. You should see the little pictorial representation switch. Then just press scroll-down/select simultaneously and the setting should stay. If it doesn't then something is definitely wrong.
Or you could just use Ken's suggestion and fly the plane inverted all the time.