the os 50sx ringed shares the same crankcase as the .40. the difference between a .40 and a .46 is actually a very big one, and the distance between a 40 and a 50 is a lot. the 50 ringed is a great engine and i would highly reccomend it. same engine as the 40 fx, just a ringed piston and tons more power. you will definatly have unlimited vertical.