In my Avistar ARF with an OS 46AX, I found I prefer using an 11x4 or 11x5. I liked the 4 better because I could do so neat stall tricks with it, and I could take off in about 30ft. And I had added an extra 8oz. of lead to balance it, instead of moving the battery. You will love the Avistar. Easy to fly, you can do many great tricks with it, and its just plain fun.