Bill,

You shouldn't need much movement of the control surfaces to get good performance from an Extra; especially the elevator, as they tend to be very pitch sensitive.

About 40% (that is minus 40% on a Hitec) is about right to get a good amount of exponential to make the middle of the stick movement noticeably less sensitive.

Don't overdo it though, as at higher percentages, the last few degrees movement can get very sensitive indeed!

-David C.