Ed Moorman did an article in RC Report about the tip fences several years ago. They lower the stall speed to a degree. He tried several configurations. Maybe someone out there has the article in a file. As I remember, a fence about 1/4in all the way around the tip worked fine. Also if you are stalling straight ahead on landing, you can learn to reduce the elevator and land parallel to the ground instead of holding the flare nose high until it drops to the ground. A side benefit of that type of parallel landing is that you will look like you know what you are doing instead of crashing to the ground and spreading the gear.