RE: Dual Rates
I'd suggest using th 1 1/4 servo arms, if that will give you your 40 degree throw on the elevator. Then you can dial your ATV down from 150 percent to about 110 to 120 percent. Set your trim resolution to 1 percent after your first flight. As long as your linkages are fairly tight, it should work. I have a similar setup on several of my planes.
Good flying.
Don