Ron,
It's tough to get a smaller boat to sail correctly, at least I have not had much luck. My cutter is 45" and over 30lbs, so I don't think my build will be of much help.

Looking at your hull and keel design, typically the prop is in front of the rudder. You would probably have to cut out a half circle in the rudder, check out boats of this design...
Joe

Gypsy is 15 inches

Ron,
My gaff rigged cutter has a auxiliary motor and it works great. I can take some photos and get you some information motor and prop and on how I did it. What size is your Gypsy?
Joe