I had a YS F-120 on my H9 cap and it flew it ok but it didn't have the unlimited verticle. This was just to much plane for the engine. I also have a world models extra 300 120 with a on os 120 4-stroke that is powered very well and is only slightly smaller than the cap. I know that the YS has more power than the OS so the YS should fly that plane very well. The reason I bring this up is because World models makes a cap of the same size as the extra and I think that would be a great airplane for the YS 120 you have. Just my thoughts. My YS just has a strait pipe and boy does it sure sound good!