Bigger plane doesn't necessarily have to mean heavier airplane. Larger airplanes have larger wings, meaning more wing area, which contributes to help keeping total wing loading lower, which is what we are interested in. If you have looked into the history of the event, the size of models have been up and down as trends develop, culminating in perhaps the largest competitive stunter in Windy's Sweeper. Do a search here on the forums and you can read all about the model, I don't think there has been a competitive stunt model bigger than the Sweeper. This was at a time when the trend was going larger in the thought that they presented better to the judges among other things at the time. Size trends have swung back the other way a bit. Smaller models can do a good job, depending on the guy at the handle, with Todd Lee and his eighth place at the NATS this year with his "flying test be concourse winner" powered by an LA.46. The size and weight of a model have really no basis in line tension, although a heavier model will pull more, but if the model isn't trimmed properly, it can get slack on the lines at the wrong place very easily. A successful model is the total sum of all it's parts, model design, properly tuned power plant, and a pilot who understands what he sees and feels when flying it. You can take the model Paul Walker won the NATS with, and give it to a intermediate or advanced class flyer, and it won't make a NATS champion out of them. Model size, for a lot of people, is dictated by how much room they have to build, store, and transport the airplane!
Type at you later,
Dan McEntee