Is your victorSlave always following the talonMaster? If so, then you should perform all that configuration one time when the objects are instantiated and configured.
Regarding the negative set point, you don’t need to do that. The most important thing you can do is set your motors and sensors in phase with each other first.
Meaning, positive input to the talon produces green LEDs, and negative inputs produce red LEDs. Then, green LEDs produce positive encoder increments, and red LEDs produce negative encoder decrements.
Once you have the motors and sensors in phase with each other, then your setpoint is the same for both sides. If you have inverted the motor in the talon configuration such that both sides of the elevator are producing green LEDs to have the elevator go up, and red LEDs have the elevator go down (or vice versa is fine), then your setpoint is just a number relative to where you are.
We treat the zero position for our arm as 0, and have the other positions be positive set point values relative to 0. That way we can reset our relative encoder when the limit switch at the bottom is hit, as well as enforce soft limits in the talon itself to prevent over driving as a fall back if for some reason we have ended up in a weird state the robot subsystem wasn’t expecting.
Back to the original question, our drivetrain is setup with two sets of motors inverted relative to each other. Here is a link to our drivetrain that shows the configuration we use after we took the steps found at CTREs documentation to make sure the motors and sensors are in phase with each other.
If you peruse the rest of the code, you’ll see the DriveMM commands we use set the setpoints of both motors to be the same (i.e. not inverted from each other) because our motor controllers and sensors have been configured to be in phase with each other on both sides.