I woulnt consider the YS is in any 50 size 4 stroke class. Nor would I reconmend one to a 1st time 4 stroke buyer. That being said, I dont believe there are any bad 4 strokes currently being manufatured today in this class rang. You'll be happy with any you choose. The magnum is a great price 4 banger if you want low investment for a good runner. Saitos are my personal choice. Love all my .56s. Works well on 40 size airframes. The 72 could be a better choice depending on the airframe and flying style. Just watch landing gear height issues on 40 size birds.