RE: Spektrum DX7 voltage
G'day Ed,
First I would copy that model to another memory slot, rebind, & check the voltage.
When I had a DX7 it didn't matter what memory I was on, the voltage showed the same.
Also, If your plane is twitchy, forget Expo, for a minute, reduce the throws with dual rates, use the low rate, at 10% less than you have now,
& fly it, if it's still too twitchy reduce the rate by a bit more, then when it's comfortable to fly, maybe then you might introduce a small amount of Expo.
Expo is a fine tuning adjustment, it is not a cure all, because when you reach the Expo point, you have full travel & it's even more twitchy.
If you start with reduced thows, you can easily go to a high rate, with flick of a switch, if you set it that way.
Cheers