Spent a bunch more time digging and now I can answer my own question:
To add a fwd elev mix to left rudder, I did a complex mix add to the Elev with a >0 curve and small positive offset. I had to reduce the scale to 40% to get a small enough change.
To add rev elev mix to right rudder I did a complex mix add to the Elev with a <0 curve and small negative offset. I also had to reduce the scale to 50%.
Disclaimer: This is for my FBL 70 which has nicked blades and a 4x glued swashplate, and may need to be re-adjusted when parts are renewed. At first I tried to add a Elev mix to the Rud which seemed more logical, but it was very squirrely. So I added Rud mix to the Elev. I consider this to be a functioning work in progress.
regards . . . g
Different fly for different guy.
