Bill, you may want to consider lightening the airframe as much as possible. Since electrics don't put out the vibration that their glow counterparts do, you could get away with a much lighter airframe.

As a rough guess without knowing all of the dimentions etc, at 9-10lbs you're looking at a very high stall speed.

IMO with that kind of weight you'll have to go with speed 600's direct drive with maybe 8x6 props.

mkirsch hit it right on the head about wanting to run as big a prop as possible, but with that much weight you may have to stick to direct drive to achieve the pitch speed to fly the plane.

If you could cut the weight to 6-7 lbs you could possibly go to speed 400's with a 2:1 or 3:1 gearbox and run 10 or 12 inch props and take better advantage of the power available.

As an example, I fly a 72"ws twinn with AUW at about 3 3/4lbs on geared 400's. It doesn't fly fast, but is very stable with flights that average about 8 minutes on 16 cells.

Good luck and keep us posted.

Jason