I had a 503 windless a few years ago that I bought second-hand. It cruised at 70 mph

I hated it because of the wind rush and I prefer to fly slowly and watch the world go by... I took the battens out of the wing and realized that they had been re-profiled significantly flatter than the original spec.
Once I had finished bending back to their normal shape, the cruise speed came right down to 50 mph.