I guess that still leaves the deadband as a variable in my situation. I am hoping someone will say the deadband should be the same for the servos of the same make/ model, but I suspect that may not be the case.
You're right. The deadband/backlash of servos, even same makes/models will not be the same. Along what these other guys were saying: Every piece of these servos are made within certain tolerances. For example: a shaft diameter might have a tolerance of 3mm +/- 0.02mm. This piece could have a diameter between 2.98 and 3.02 and still be acceptable to the manufacturer. When you have dozens of parts all with their own tolerances, all falling in varying spots within their tolerances, and then all being assembled together in different combinations of variance, you're not going to get results that are exactly consistent.
My advice would be to set a target tolerance for positional accuracy of your device then work from there. Setting a goal of "exact" is only going to frustrate you further.