Funny I just flew this combo last week. I decided to try out the ST 2300 on my Zero 71" that has originally a YS 120. Much to my dismay, the power was not any greater than the YS 120. The nice thing about this combo is that the engine is completely hidden when you mount inverted and use BCM inverted muffler. The muffler corner does stick out a little, but not bad. Also, I didn't add any lead weight, and it feels like the aft-end of acceptability.
And yes, with this power it can hover, and I've done it with YS 120. If you go with a Saito 100, it will fly, but you will need to stick another Saito 100 somewhere else in the cowl to balance the plane.
