It would seem a hollow victory to win with someone elses' creation. I am not saying that I haven't made a career out of stealing other peoples' ideas though. But it is still fun for me to compile the best ideas and then try to come up with my own version.
At the end of the day, a win is a win is a win, there are alot of good designs with none of them being a dominate design. I do agree with you on the pride of flying your own designs, that is a big part of it for me as well. You have builders and you have flyers, its all good! I started out buying 3 different kits, just to see how they were put together and to get the instructions that go along with the kits. I've stolen many of these ideas and cobbled them together into something I finally feel is competitive on any level. It only took a year to do it, with many diversions along the way.
The biggest part of making a competitive design was to fly it enough to know where the c/g was, and what was an acceptable range. Once dialed in, most any place can be competitive, but if your not comfortable with its tendancies and you don't have the c/g figured out correctly, you'll never place high, no matter whos design your flying!
Also, I like a 60" wing in SSC, at those speeds, they roll better than the longer wings...