That is indeed another factor, Chris - performance creep. (That's different than rules creep.) This happens in all of our classes as a sort of natural selection as drivers tend to choose cars that are marginally faster. The imaginary "index" of performance rises.

To suggest that the classing process has changed over the years suggests that there used to be one process, and now there's another. In fact, there have been perhaps dozens of ad hoc processes applied (as opposed to Ad Hoc Committee) over the years.

K