I love my 40 size gp extra, and originally flew it with a little 52 Magnum 4 stroke. Needless to say it was underpowered, but a great flyer none the less. I currently have a 61 Magnum 4 stroke in it, and with everything slid forward it needs no nose weight. I have a fairly large fleet of Planes and this is one of my favorites. The kit builds nice, and the Plane is a good flyer! A Saito 72, or Magnum/O.S 70 4 stroke would be about perfect for this Plane IMO.