Flew my first flights today. Had two experienced pilots with me. The new bird flew great but had a flutter that only appeared to occur out of a shallow dive, not high speed and not under power. The other pilots said a couple of things about the linkage, but it appears to be slop free. One of the pilots pointed out that the servos did not appear to be locked in, in other words, they had play around neutral center when they should have been rock solid stiff. Ther servos are Hitec HS 512mg. No other problems, flew well and didn't even need to trim it. But, this is my first fixed wing and I could have overlooked something newbe-ish, so veterans, please help me out.
Attached are photos in case that helps.