I have a bunch of Saito's. Never had any problems with any of them. I would reccomend a 56 or a 72. The 72 is if you want a bit of excess power. The 56 would fly it fine. I also advise against the YS. They are a great engine. But can be a bit difficult to set up. Once set they are fine. I do not know about Magnums, never had one. I would also say the OS would be fine. But I still say that Saito is the best first 4 stroker you can get. Good luck with whichever one you end up with.

Mark Shuman