I used a 14x4 on my Hog Bipe, with the .91 OS 4-stroke. That was not the first propr I tried, but it was the one that really made the plane
work well for me - especially for nicely controlled approaches and landings. I can come in slow, the plane seems to just sit in the groove, were the prop is probably creating just a small amount of thrust and yet the engine will be quite responsive to the slightest throttle changes. This aircraft can land in a very tiny area! I watch so many folks come ripping in to land, with various planes, fighting the thing down, careening along the ground or just above it, sometimes running out of room - every time, I seem them using a x7 or so prop. I suggest that they drop down to a x4 pitch and perhaps up 1 inch in prop size, just to see how things work out. Unless you really, really need exceptional speed, you get better take-off/climb performance, smoother aerobatics and easier approach/landing. Of course, that is just my opinion and experience - "Your mileage may differ". At least, don't be afraid to experiment, don't just go by the engine company's suggestions and/or "conventional wisdom". For a lousy $5 or so, you may find out that trying a new prop may give you a totally new airplane. I have had this happen with several aircraft, from .40-size Taubes, up to Senior Telemaster, and several in between sizes. Good luck!