RE: Seagull Models Zero ARF - Online Build
water.boy, I have a Magnum .91 4-stroke in our SG Zero, we still had to put 4 ounces of weight on the firewall, and the battery is mounted on the left side of the firewall box. Our CG is 1/4" behind the main spar where the wing joins the body. The plane flies really well, just be ready with some right rudder on take-off. The Japanese Zero with its short nose requires some weight up front to balance correctly, that's why we went with the heavy engine.
Best of luck with yours, regards from old bird.