Interesting. When I did RUD->RUD, I could not get the VR to work as the OP described. However, by doing the RUD->AUX1, it did perform as noted above. Further, I was able to use point curves or expo in the mix AFR to get a non-linear servo output response from the rudder stick based on the position of the throttle stick.

I'm using a Futaba 12FG with Ver 2.1 software.

r/s... Roger Parrett