a 9x8 will run on a .46. That's getting into pylon racer size, though. If the model is heavy or draggy, it will take forever to get up to speed, and it might be VERY fast. For that plane and a .46 engine, I'd go with a 10x6 or 11-6. It'll be plenty fast for swcale-type flying.

Remember: GIVEN THE SAME RPM - more diameter/less pitch = more pulling power, less top end. More pitch/less diameter = less pull, more top end.

Dr.1