don't worry too much about SAC results.
I did BM last year and after receiving my statement of study score, they ended up scaling highly (based on exam performance)
Unit 3 internal score: 89/100
Unit 4 internal score: 84/100
Unit 3 internal score (after scaling): 99/100
Unit 4 internal score (after scaling): 100/100
So basically, if you don't do as well as you would have liked to in terms of your SAC marks.. don't stress because your exam is weighted far more heavily (even though VCAA state that the weighting of SACs vs End of year exam is 50:50). In reality this isn't true because your SAC results get weighted upwards (if your exam result is high).
For those interested in what kind of exam results you need to score highly...
I scored 115/120
Note: The exam is out of 60 ~ (57.5/60)
Study Score: 49
Note that the A+ range was from 101/120 (from memory).