I have 2 with Saito .91's. I think that the perfect combo would be the Saito .72, I don't know about the YS, I haven't flown one so I don't know what prop you're swinging. There was a world of difference between mine with a .91/14x6 and my buddies .61 with a 12x6. The four stroke was much better suited for 3D...
Maybe the .61 would work better on a 14x4 or 5?
The bigger props throw a much larger thrust column so it's easier to vector the thrust during hovers etc. With the 14x6 you could maintain a knife edge at a much slower velocity than with the 12x6. It sounded like a snare drum with the 2-stroke too.
Chris