I think I may have fixed the prob with the ds811. I have been testing tonight trying to figure this one out. It appears that it does it only at the center position. I could flick the rudder and it would start vibrating. I started adding subtrim and it stopped at around 10.. I added 10 more and it does not do this anymore. I have the UCD .60.. so.. it has a very large control surface on rudder that was causing the problems. After adding the subtrim.. just twisted my clevis a few times to make that the center and it works fine. I am not saying I lie this..but.. it appears to work. This worked with trim too, but, did not want to waiste trim steps until I was in the air and needed them.