I had a YS-45 in my Sceadu 50 for a short period of time. The pump found a soft spot in the tank during first flight and it ruptured. My OS-50 arrived while I was waiting for the tank so I switched it out for a couple of reasons. The engine had an irregular pump issue and is the older system with only a main needle and no idle mixture screw. Setting the pump screw was more trouble than it was worth to try and find a happy medium to get it to idle. I would love to see them produce a 50 size heli version.