This will save you time and effort as with one click of the mouse (after you have followed the simple tutorial) you can adjust your expo to your liking and to suit the model you are flying.
Simply tweak and re fly and re tweak if needed....
And another grand in servos, motor, esc and batteries lol. OH, plus extra battery trays (if the 770 uses them) if you want to run multiple batteries. More than I have, but would love to have one if I had it.