Design your registers so 180° of servo travel is necessary to move the damper from fully closed to fully open position.Primary reason for this is that the torque required from the servo is proportionally less, hence, less stress, longer usable life and quieter operation - servos are becoming to growl as the load goes up, and as their age goes up.
There are several things you need to keep in mind when you're designing products using servos.
Servo range of motionAll servos, being analog devices, are different. Normally, servos are supposed to work with PWM control signal being between 200μsec and 2000μsec, but there are instances that can go as low as 160μsec and as high as 2300μsec.
Servo controller signal rangeNot all servo controllers are created equal, either. Some of them support advanced range limiting and calibration options, some of them are incapable of producing anything other than a predefined range of signals with no calibration options whatsoever - the only calibration option would be to design the device in such a way that the servo travel is artificially limited, and later use software controlled range limiting to make things work properly.
Hardware vs. SoftwareDZ3 will support both range limit and calibration within coming weeks (DZ2 supported it already, and it's just a matter of porting it over), so your hardware (both servos and controllers) is the only limitation for your design.
On the picture: existing register designed to utilize 180° of servo travel.