I have a YS 91FZ on my 4*60 with an APC 15x6 and it is the perfect combination. I have flown others 4*60 with a saito 61 which was fine, but lacked significantly in the powerband. The YS may be a little too much, but throttle control is no big deal. With this motor, I can hover, knife edge, waterfall, etc... I also modified the rudder and added 1 inch extra to the rudder and elevators. Dual servos on the elevator also, with a pull-pull rudder set up. A Saito 91, 100 or OS 91 will also fly these fine. But all these are 4 strokes and you mentioned a 2 stroke. So any powerful 2 stroke above a 60 should fly the plane fine, but I would still recommend considering a 4 stroke.