I have the saito 100 on mine and love it. As far as YS goes yes typically a YS will have gobs more power than engines of equal, but are known for being a bit fussy. My saito 100 will idle forever smoth as can be and pleny of power for this plane. my vote is for the Saito and if you wish to move the fuel tank over the CG then I would get a pump for it. Otherwise leave it as is.