i also believe you should stick with the .40 size case the .60 size engine will be a little on the heave side. the Magnum will be on the light side though. If you slide the motor forward on the mount all the way and try and put the battery under the gas tank. I put a heave spinner nut on and opted for the battery and reciever right behind the tank with the motor slid all the way out on the mount. I used a GMS .47. without the nose weight on the plane it flies about the same as with the weight on but it lands nicer with the weight on "not quite so much floating" what ever you decide to do have fun flying