ORIGINAL: Hobbsy
John, what you're experiencing is more accurately called'' tortional impulses'' caused by a light engine, flexing mount and powerful power pulses. Set everything up as stiffly as you can, for example H9 aluminum mount, wing bolted on tightly etc.
Great advice. I changed the mount to an aluminum mount. Had to redrill the mount holes in the firewall (not a problem). Just got back from flying and everything was great. No wind for a change. I made a mistake in the previous post. This is the Spacewalker II 1.20 ARF from Horizon Hobbies, not the Sig Spacewalker. The Saito 1.80 really pulls it through the sky. Most flying is done at half throttle. Thanks again for the advice, Hobbsy.