I had a 4 star 40 that was built as a club racer. It had a Rossi 45 with a pipe on it. Extremely fast. When I was Sport flying it, not racing, I took it way, way up and then streaked down. I'd guess it was going way over one hundred mph. Level it out about 10' off the deck and the wing just kinda exploded. It wasn't like it broke in two pieces it was more like it desenaragated. I always thought that if I had sheeted the leading edge of the wing it may not have done that. Maybe maybe not. In any case it was a clear cut case of exceeding the flight envelope it was meant to fly at.
I guess I'd consider what engine your going to use and how you intend to fly it. As a sport model there is nothing wrong with the origional design. It's tough to beat any of the Sig 4 Star models.