I've got 2 DX7S's and love them...
if I'm experimenting with a particular setup and assuming I haven't filled the TX up, I'll use the COPY function to copy the airplane's profile to a new (blank) profile.
(giving it a unique but Similar name... say 'Sbach' and 'Sbach3D')
I can then make changes to the Sbach3D program... changes that work as expected are then made to the Sbach profile, changes that don't work as expected are removed from the Sbach3D profile. (alternately you can also copy the original Sbach profile to the SD card.. in case you want to revert back)
also don't forget when setting things like D/R, Expo, servo travel etc, you need to set it in BOTH stick directions, and possibly with which switch (example, if changing elevator travel, remember to set both UP and DOWN travel, if setting expo, remember to set it either by flipping a switch, or set it to be 'ON' all the time)
+1 on READING the manual gobs of information in there!