I have a question, Matt.
/snip . . .
Is the Hobie 16 a One Design class?
Absolutely. The 16's original rudders came from the 14 (ABS). They didn't prove to be up to the task, so the class rules were changed to allow rudders of the same profile, with thickness and weight restrictions, but made of any material. All of the other rudders fit within the class rules.
The plastic rudders are pefectly fine for the vast majority of sailors - they're relatively inexpensive and durable. The racer and EPO rudders give better control at higher speeds, but at a considerable price increase.
You're also condensing nearly 40 years of class development into a paragraph. There have been many minor changes to the 16 since its introduction that if you lumped them all together, would be a major change.
However, you could sit a 1970's era boat next to a 2009 and you would still know that they're both Hobie 16s
This situation is no different (and in some cases even more restrictive) than any other one-design class.