Thanks to all of you for excellent suggestions. I am going to take the advice and really focus on making sure the elevator halves are really in synch and moving the same degree of deflection. I will use the balsa sticks / toothpicks to really try and fine tune the two halves. I am also interested in the comment in the one article about not using 2 channels and mixing but using a Y connector etc. I had a close look at how the elevator halves are moving and I think there is a discernable difference in speed of deflection between the two sides. To my eyes I think there is a delay or one side is moving slightly slower than the other. This must have something to do with the 2 channel mixing and master / slave functions. Should be a fun weekend working through all of this. Thanks again, I really appreciate your thoughtful responses. True test of this will be back in the air !!

Bill