How to reverse servo out put in quad copter mode?

I am working on a project that uses servo controlled puffer jets to stabilize the aircraft, but in quad copter mode you cannot change this setting, I was going to use a Y harness to control both pitch and roll puffers but as you increase throttle it would close one puffer and open the other. I used all 4 channels and it fixed the problem but now I need to reverse one roll and one pitch servo how can I do this, the software does no allow for this.

What are you using "all 4 channels" of? What is in "quad copter mode"? It doesn't sound like any Arduino I know.

If the two servos concerned are on the same Arduino pin then you cannot reverse the direction of one of them by means of control from the Arduino

If the two servos are on different pins then if you write a value to one of them and 180 minus the same value to the other then they will move in opposite directions