I switched between YS 1.40DZ/1.60DZ and OS 1.40RX in my first Partner seamlessly with a Hyde ARA (AR mount with aluminum beams that only captured the rear two bolt holes). That was my favorite mount Merle made. Your only issue between the OS and the YS may be header interference with the very top of the mount. I always used an Asano flex header on the OS, so I had no issues, I know a friend of mine had some problems with the stock OS header when he put an OS in his Brio that was built for a YS.