I would suggest you do around 3-7 practice exams, if you wish to aim for that score. I recommend you doing the VCAA papers from 2008-10 FIRST, then perhaps try the recent Kilbaha, Heffernan, and MAV papers if you have time. They're my favourite companies for methods papers. You should definitely do a few 2011 trial exam papers, if you manage to get your hands on any. If you're interested, you could msg me your email address and I'll try to send a couple to you. I only have MAV, and Heffernan 2011 papers, though. But I reckon that should be enough. I'm doing at least 2 from each year (2006-11) regardless of the company, since I'm aiming for 43+, so yeah...
Also, for last minute revision, there are some very useful methods resources you can find under the Notes section of AtarNotes. Look at the bound notes, or any summaries, skim through them, and focus on the areas that you are struggling in most. And THEN, go through the basics/stuff you're already familiar with, and the common types of exam standard questions. That's why I suggested you doing practice exams.
Hope that helps
