RE: GP viper and 46FX
If you are using expo, there is no real need to switch between the high and low rates. The plane should respond well in either rate. You may have used too much expo if they are at 60% and 80%, this would make the sticks feel like there is no elev response until you get to near full stick travel. I don't even use that much expo for 3D deflections! The control surfaces are small and don't have much deflection, just use a small amout of expo to smooth out the plane when using small stick movements.
I use a low rate if I want to fly and make turns using full stick movements, but I generally like to fly on high rates with expo.
I do use a landing mode with a little more expo on the elev to let me feather the landing flare.