How to make a servo-based control surface do pitch and trim?

[cantab]

I have a plane with an all-moving canard, a delta wing piece mounted on a servo, that want to use for both direct pitch inputs and for trim or something like it. (This plane, https://steamcommunity.com/sharedfiles/filedetails/?id=2796094084 and yes I know you can see a hinge, the rotation servo is underneath that.)

So I want a single servo to respond to a direct input - press one key it goes fully one way, press another key it goes fully the other, let go and it goes back to the neutral position - and to be able to set the "neutral" position incrementally. Is there a way to do this in stock? If not, is there a mod that can provide this functionality.

The servo is set to range from -20 to +20, with 0 being the position that puts the canard flat. I have tried all the following and they didn't do what I want:

• Binding the servo's Target Angle to Pitch in absolute mode. This gives me direct pitch control but no trim. As previous forum threads have discussed, trim and SAS ignore axis assignments.
• Binding the servo to Pitch in absolute mode and to Custom01 in (inverted) incremental mode. The absolute mode "wins" forcing the servo to 0 when W or S aren't pressed regardless of what I do with the custom axis.
• (Binding the servo only to Custom01 in incremental mode. This provides trim functionality, but no direct pitch control, and therefore no way to do sharp manouvres. I mention this to show that Custom01 and incremental mode do work by themselves.)
• Binding the servo to a single KAL controller (with position -20 at the start and +20 at the end), and binding play position of that KAL to Pitch in absolute and to Custom01 in incremental. Same result, absolute wins. I see this in the play position of the KAL controller, inputs on Custom01 don't move it from the 2.5s (midpoint) position.
• Binding the servo to two KAL controllers, "Canard Pitch" and "Canard Trim", with the same track set. Then binding the Canard Pitch controller to Pitch in absolute and the Canard Trim controller to Custom01 in incremental. Setting priorities:
  • Equal: When I am changing the Custom01 axis the canard moves, but as soon as I let go the Canard Pitch controller "takes over" and forces it back to zero if there's no pitch input or full down/up if there is pitch input, regardless of the play position on the Canard Trim controller.
  • Canard Pitch higher number: Only Pitch takes effect, Trim does nothing.
  • Canard Trim higher number: Same as when they were equal.
• OK so I'm adding a third KAL controller, call it Canard Pitch 2. This one is set to control the play position of, enable, and disable Canard Pitch. Play position track from 0 to 1, Enable controller track at start and end, disable controller track in the middle. Canard Pitch 2, and not Canard Pitch, is bound to the Pitch axis. That doesn't work either! It turns out that when the Play Position on a KAL controller "jumps", whether that's by an axis (either absolute or incremental) or by clicking the slider in the part window, 'instantaneous' actions in the KAL tracks such as enable, disable, toggle, etc do not trigger. Those actions can only be triggered by Playing the KAL track.

So that's where I'm at. All these things that don't work and I'm just about out of ideas.