As a few people have mentioned, the Big Stik 60 tends to be nose heavy. One thing you can do is mount the engine closer to the firewall than specified in the instructions. Leave just enough room to route the fuel lines.

The most common .61 to .95 two strokes have the same size case and mounting bolt pattern, and the weights are usually similar. So, you can use a wide range of engines and a 90 size is at the top of the recommended range according to http://www.greatplanes.com/airplanes/gpma1220.html Engine Required: 2-stroke .60-.91 cu in or 4-stroke .91-1.20

Carrell