In the current state, all the custom controls (Slider 1 to 4) are auto-inverting their effect on control surfaces when a mirror operation is applied to it.
When manually selecting the input axis from the non-standard set of inputs (not one of Pitch/Yaw/Roll), it must be a selectable option whether to invert or not to invert the input axis when a mirror operation is applied.
Something like this already exists for steering on wheels, but is missing on Control Surfaces.
This is a hard requirement when using control surfaces for anything other than the standard Pitch/Roll/Yaw operations. Specifically, this has become an issue when trying to construct a propeller with control surfaces for AoA tuning. When mirroring the prop to invert the direction, this immediately also results in inverting the direction of the control surfaces. (One rotor ends up incrementing, the other decrementing the AoA when both should have done the same.)
Also for flaps / spoilers / airbrakes when assigned to spare sliders