[dmcquinn]

My 35% Yak would do this at high speeds. There was a slight slop in the pull-pull system. Basically, I had it set up so that the wires got slightly tighter when the rudder was deflected and at neutral the wires were a little loose. I'm talking about maybe 1 mm of slop (less than 1/16 inch) at neutral. But correcting this fixed the tail wag. I have two 5955TG servos so there is enough holding power.