This has got to be one of the most useful functions on your Transmitter! Expo deadens the response of your control functions close to the centre of the stick.
Lets put it another way, suppose your elevator stick has 25degrees of back(up) movement, and obviously the same forward(down). Lets suppose your elevator has 25degs of up and the same down, with no Expo you have to be extra careful when you move the stick, otherwise your plane will be all over the sky (I've lost a couple of models this way, cheap TX, no Expo=overcontrol)
With say 50% Expo, when you pull back 5degs on the stick you elevator only moves maybe 1, at 12degs it's maybe 5degs, but when you pull all the way back you get your full movement.
With a new model I find 60% Expo softens the centres nicely, just remember Futaba needs - or negative to soften things up, all others need +
Do it now, you may never get another chance
