i have the os 70 surpass in my ucando 46, and a digital mg servo on the rudder, the os is 5 oz. heavier than the saito, the mg servo in the tail is 2.11 oz. w/ the battery all the way forward, i got the cg to 4 3/4". you'll be around 5" w/your engine, that should be a good placement.
jon b