Sorry, brain fart on my part.
Yes, the CS is outclassed in SS. But in regional competition, I promise you that you can usually still do okay against a lot of those guys with good enough driving. I've beaten a LOT of SS cars and such in a C-stock Miata and Toyota Spyder, believe me.
The problem with the CS is that it is too good for AS and not good enough for SS and there's nothing in between. So it would take some pretty special driving to even trophy at Nationals in a CS in SS. But a base Cayman did trophy in AS. But again, most regional events don't see that level of competition, so in a class like SS even if one or two really good drivers show up in better cars, you're still likely to have folks there you *can* beat.
And since we know the CS would be an overdog in AS, don't worry about being an underdog in SS until you're beating all the AS times.
--Donnie