Just don't buy the engine from whatever mfg you found that produces a 30 oz twin. The Saito FA-90TS weighs just 25 oz, while their .65 single weighs just a fraction of an oz under 20. Not much difference when you consider that any plane big enough to have that engine mounted on it will be longer and have a bigger wingspan to offset a fatty engine. Just my opinion, but I am almost done building a SIG 1/5 scale Cub with an 84 1/2" wingspan and I am mounting the FA-90TS on it for power. It should fly very scale, look really cool if I don't screw up the cowl, and the sound will be great.

Lachlan