I have a YS91AC on my 60 SDK. I used to swing an apc15x7, but I'm trying a Zinger16x6 right no. With servos mounted per plans, mine came out just a tad nose heavy, but I haven't added weight to the tail. Compare the weight of the Saito120 and YS91AC/FZ and it should give you a good idea. A Saito120 will not be to much, and don't worry about prop clearance, for some reason the aluminum under carriage comes bent in a way that makes the nose very high. It is a great hovering plane, when doing elevators and harriers it needs some spoileron to keep from rocking out.
DKjens