Turtle Decks

I have been looking at some photos recently and I have noticed that some supercubs have a pretty flat turtle deck and some are curved. Were they manufactured this way? I thought the curved ones were just in need of new stringers but it appears that is not necessarly the case. Am I seeing things or are some more curved than others?

Grant, I'm not sure if this is what you are asking, but the PA-18A models had no curved turtledeck, while the PA-18's did. The "A"'s are often referred to as "fastbacks".