AbuF,

I'm no engineer, but I wonder if the old sliding servo idea could be adapted to your problem. I personally never used it (a Christy mixer was easier to set up), but as I recall it was used on ruddervators where (I think)the rudder servo was moved back and forth by the elevator servo. The movement did not change the rudder function, but caused them to move up and down in unison for elevator action.

Like I said, I'm no engineer and I can't really visualize your challenge, but them above came to my mind. If it helps, nobody will be more surprised than me (-:
Walt

PS you DO post some of the most intersting challenges. WT