I had an Ultimate-30 that flew with a Saito .40 then a .50 and finally with a .56. It was a blast on all three and was best with the .56. Never did kill the plane, just sold it and for all I know it's still giving an adrenaline rush to it's owner. A .46 2-stroke or a .56 4-stroke will give you all the performance you want and be lighter than the OS .52 (and you still have a throttle for those calmer moments).

I replaced the landing gear with a larger unit, but kept the wheel pants. It's a super plane!

quint