I had this plane and powered it with a YS120FZ. The plane was a monster with that engine. I had modified the plane such that I used two elevator servos and mounted them in the tail where the elevator pushrods were supposed to exit so I didn;t have a CG issue. I've flown the plane with a YS91AC. It still had unlimited very with the YS91, but I personally prefered the YS120 setup, but the plane was a bit heavier with the 120. My guess is the Saito 120 has power somewhere between the YS91 and YS120.

You pointed out the exact same thing I had to think about. Is the extra power worth the wing loading. I can tell you that my YS91 setup gave me a much more nimble plane because of the lower wing loading. I decided to use the YS120 and sacrifice some agility for raw power.