Hello Pawel,
I'm not familiar with VPlane or Jets, but since agility is the same as dual rate on conventional radios, dialing it down to zero should dial down the roll rate to zero (and subsequently, the spreading of the overall stick travel from center to max. rate). Expo then shapes the curve.
I mean, you can always use one bank even for extreme tests (like zero, or _very low_), to see what difference it makes.
I can hardly imagine that the model will still react twitchy, then.
What you could also do: make the physical connectors CH2, CH3 (I assume) curve cells, 7-points, and adjust manually, and use FC Aileron as an input.
For testing/setup purposes, you could even make that switchable, make the connectors Multiplexer (Mux) cells, assign a free switch as the selector, and set up three different curve cells, or two and leave one genuine FC Aileron (safe/known).
—Eddi
Born to fly ...
forced to work.