You would be just fine to put the Saito .56 on the Ultimate. .48 or .56- Not much differentce there... Not only that, but most people over-power a plane anyway! I had TWM Ultimate 1.20 (recommended power 1.20 4 stroke) with an evolution 1.20 2 stroke on it. She flew very nicely with no bad habits! Good Luck- I hope this helps you out!