Apparently its generally rank 1-3ish who don't get affected?
It depends on a lot of things, really. If you're ranked first with a 100% SAC average, even if you do well on the exam, that mark is likely going to get scaled down, even if you're in a pretty strong cohort (unless you do extraordinarily well). It's not as if strong cohort = marks scaled up and weak cohort = marks scaled down. It is generally the case, but that's because marking tends to be more harsh with stronger cohorts and much more lenient with weaker cohorts. If you're performing well in a weak cohort (and everyone is else is doing crap), in all likelihood your cohort's SAC scores won't be scaled down at all, even though you're in a weak cohort. Moderation is mainly to take care of discrepancies in marking leniency/harshness, rather than cohort strength. Even if your cohort is weak, it doesn't mean your marks will be scaled down, just as being in a strong cohort doesn't guarantee that they'll be scaled up.
It depends on a lot of factors and it's hard to predict anything. We're only just over half way through the year - most of the assessment is yet to come. Just focus on doing well and let the technicalities of the system take care of themselves.