scaling plays a rather large role for SACs, for example I have heard rumours that a C+/B from MHS goes up to A/A+ [pretty much riding on this

] But as the other guy said, don't stress too much because your exam plays a MASSIVE role, ace the exam and your SAC scores mean little.
Anyway, writing HEAPS of essays is not the way to go about it, well maybe with the exception of Language Analysis.
Personally, I think the key involves making sure you can address everything they can throw at you, so for your text response, there are maybe, 4 or so themes, most will have overlapping areas, just make sure you are able to write 4 paragraphs about that, and have relevant quotes at your disposal.
It is similar for Section B, the topics may be somewhat broad, but all ultimately ask a very similar question, preparing only a few essays should be ok here.
But the main thing is, revising these essays and say, if you are getting an 8 or so, improving and editing them so that they are really good, and even if you end up writing a different essay, you should be able to identify the mistakes you had made, and not make them again, or whatever is appropriate.
-note that I suck at English, just this is what I think is a good approach