I have to agree with Fred, and just to let you know, you have to slow it down for landing before you make the first turn to final. Otherwise, you just have too much speed. If you have good throttle management, a 12 x 4 may do. Likewise, you may find the 13 x 4 better, just don't expect too much from the motor, and expect the revs to get to where they were, it wont do it, and you can ruin the motor by trying to lean it to get there. Truely, the 12 x 6 shouldn't be a problem, but like Fred said, you can experiment, just be careful. The plane will float, no matter what prop you run. I slow mine down way in advance, and bring the throttle up one or two clicks to stretch the landing / glide slope out. Good luck!