Wow, lots of varying opinions here.

Scott, just finish the plane with the 3W 75. It will work very well on that plane, don't spend any money on another engine at the moment. The 3W 75 is a great engine. Smooth and powerful.

Flying time is more important than having the what somebody else determines to be the "right" equipment. You need to realize the engine will likely generate "only" ~45 lbs of thrust instead of the 50+ from the other engines. It will still seem plenty powerful.

If anybody doubts the capabilities of a 3W 75 in a 23# plane, watch this video: http://ca.youtube.com/watch?v=UcROF4...eature=related . Granted it is Bill Hempel flying, but the quantity of power is not a problem.

If you work on the plane a bit perhaps you can cut some weight, maybe go with lighter batteries or carbon wing tube. Either of those changes will save 6 - 8 oz.

I say put the 3W on the plane, put a few dozen gallons of fuel through the engine (in the air of course) and then report back. If you decide to upgrade the motor down the road just plug the holes in the firewall and drill new holes. Chances are you will want to upgrade the airframe anyway.

Good luck!