I agree with MMALLORY
I had exactly the same linkage geometry on a 1/3 scale Spacewalker..one servo horn up, one down...
With careful adjustments I was able to get perfectly linear responses from each elevator half thru the normal range of travel...in the extremes of throw the elevators would begin to deflect slightly differently. This bothered me, I like perfection and symmetry when possible.
But the Spacewalker wasn't going to be 3D'd much <g> so I used it that way.
I expect the GB won't need 3D throws either...