Hi
When servos are matched at PB, there are only 3 points where they really match - Neutral and both end points. In my TD Hawk, I have 2 ganged servos in the stab, but I am connecting those to the PB to different channels and make the elevator function in a knob. Ithen match the servos in a PMix using 18 points in my 18MZ. Have done that in several planes with several hundreds of flights and no problems

Nuno