No offense, but I'm surprised anyone would run a zinger that big- a friend has one that he had ordered at his (our) LHS, and it looks like it would not hold together on one of these 50cc engines- I could only imagine there would be a great deal of flex in it, thereby reducing the efficiency. I would not stand within 30 feet of the plane with that prop on it! Try Toms 22A prop on it- or 23/8 bunny- you want a solid thick prop on these birds, the engine/airplane combo should have NO PROBLEM hovering, even with a red brick in it! SERIOUSLY!
Change the prop and it will be a completely different bird.

just a couple of pics from sunny California today...