I would say as westy did anywhere in the 16X4W to a 17x4W depending on throttle response 16x6 may work. Its never an exact science some times you need to bite the bullet and try a couple to make sure. As for the .63 I use a 13x4W and I am completely satisfied. Some people say a 14x4W works for them I didnt get the throttle response I was looking for where I may have gotten it from the 14x4 I chose the 13x4W. ITs a gental balance between dia and pitch for 3D some people rather have the dia vs the W in the prop. Hope this helps.