I think, after building mine and flying it, that the tail heavy planes were trying to balance about 5" back. the UCD flies fine at 6" back. But, the extra power you'd get from the Magnum would be worth using. I've got a Saito .91 in mine and I think it's perfect. I originally mounted the rudder servo in the wing opening and used pull pulls, but after flying it, I moved it back to the tail. Inverted is much better at the rearward CG. The UCD comes in between 5.5-6lbs, so the larger motor would be a benefit.