FS isn't a patsy class. It has high hp cars that lack lsd - which is a big disadvantage in autox. I also disagree that classes cascade down from SS, AS, BS, etc. It has more to do with cars, holdovers and where things fit.
Example: The G35 sedan is DS, the G35 coupe is FS. The cars have the same motor and driveline (other than shortened chassis).
Looking at national tour times (as opposed to local times, where there are inconsistent driver performances) confirm that it isn't a waterfall from A on down.
I'm looking forward to taking the 335 for a spin around the cones after I put another 975 miles on it (I'm at 25 now
. Maybe I can find a little fun run session and compare my CSP-classed Miata.