No no, there is no mixing involved, just a custom curve. This is what I use for AIL and ELE now:
It's a result of a lot of testing and works good for me. And as you see, it has a kind of "deadband" included in it. It's not exactly deadband, but it is very insensitive around center.
But having deadband included in Spirit, I think I won't be able to get consistent results in Sim and in real heli. I will test it more (we didn't have flying weather recently and I developed this in the SIM), but I imagine deadband will ruin this setup..
So deadband is OK in general, I just want to control that in the radio. Is Spirit requiring this for some reason? Could it be removed, or allowed to go lower than 4?
Also, it seems to me that controlling this separately for cyclic and rudder really makes sense.